* [PATCH 0/2] Bring includes in linux/kmod.h up to date
From: Petr Pavlu @ 2026-07-08 15:44 UTC (permalink / raw)
To: Tony Luck, Borislav Petkov, Thomas Gleixner, Ingo Molnar,
Dave Hansen, x86, H. Peter Anvin, Philipp Reisner, Lars Ellenberg,
Christoph Böhmwalder, Jens Axboe, Johan Hovold, Alex Elder,
Greg Kroah-Hartman, Rafael J. Wysocki, Michal Januszewski,
Helge Deller, Alexander Viro, Christian Brauner, Jan Kara,
Trond Myklebust, Anna Schumaker, Chuck Lever, Jeff Layton,
NeilBrown, Olga Kornievskaia, Dai Ngo, Tom Talpey, Mark Fasheh,
Joel Becker, Joseph Qi, Tejun Heo, Johannes Weiner,
Michal Koutný, Luis Chamberlain, Petr Pavlu, Daniel Gomez,
Sami Tolvanen, Aaron Tomlin, Pavel Machek, Len Brown,
Andrew Morton, Danilo Krummrich, Nikolay Aleksandrov,
Ido Schimmel, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Simon Horman, David Howells, Jarkko Sakkinen,
Paul Moore, James Morris, Serge E. Hallyn, Kentaro Takeda,
Tetsuo Handa
Cc: linux-edac, linux-kernel, drbd-dev, linux-block, greybus-dev,
linuxppc-dev, linux-acpi, linux-fbdev, dri-devel, linux-fsdevel,
linux-nfs, ocfs2-devel, cgroups, linux-modules, linux-pm,
driver-core, bridge, netdev, keyrings, linux-security-module
The usermode helper declarations were previously provided by linux/kmod.h
but commit c1f3fa2a4fde ("kmod: split off umh headers into its own file")
moved them to linux/umh.h in 2017. Add explicit includes of linux/umh.h to
files that use usermode helpers and remove linux/kmod.h where it is no
longer needed.
Then clean up linux/kmod.h so that it includes only the headers that it
actually requires, importantly removing the compat linux/umh.h include.
Apologies for the wide distribution.
This cleanup is motivated by trying to reduce the preprocessed size of
linux/module.h, which includes linux/kmod.h. The linux/module.h header is
included by every *.mod.c file to provide `struct module` and other related
definitions, so it should avoid pulling in unnecessary dependencies. Note
that this series doesn't immediately improve the situation, since most of
the files included by linux/kmod.h are, for now, also included by
linux/module.h through other paths.
Petr Pavlu (2):
umh, treewide: Explicitly include linux/umh.h where needed
module: Bring includes in linux/kmod.h up to date
arch/x86/kernel/cpu/mce/dev-mcelog.c | 2 +-
drivers/block/drbd/drbd_nl.c | 1 +
drivers/greybus/svc_watchdog.c | 1 +
drivers/macintosh/windfarm_core.c | 1 +
drivers/pnp/pnpbios/core.c | 2 +-
drivers/video/fbdev/uvesafb.c | 1 +
fs/coredump.c | 2 +-
fs/nfs/cache_lib.c | 2 +-
fs/nfsd/nfs4layouts.c | 2 +-
fs/nfsd/nfs4recover.c | 1 +
fs/ocfs2/stackglue.c | 1 +
include/linux/kmod.h | 12 ++----------
kernel/cgroup/cgroup-v1.c | 1 +
kernel/module/kmod.c | 1 +
kernel/power/process.c | 2 +-
kernel/reboot.c | 2 +-
kernel/umh.c | 2 +-
lib/kobject_uevent.c | 2 +-
net/bridge/br_stp_if.c | 2 +-
security/keys/request_key.c | 2 +-
security/tomoyo/common.h | 2 +-
21 files changed, 22 insertions(+), 22 deletions(-)
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
--
2.54.0
^ permalink raw reply
* Re: [PATCH v1] landlock: Update formatting
From: Günther Noack @ 2026-07-08 15:30 UTC (permalink / raw)
To: Mickaël Salaün
Cc: linux-security-module, Bart Van Assche, Miguel Ojeda
In-Reply-To: <20260708110635.2083515-1-mic@digikod.net>
On Wed, Jul 08, 2026 at 01:06:33PM +0200, Mickaël Salaün wrote:
> Following commit 99df2a8eba34 ("clang-format: fix formatting of guard()
> and scoped_guard() statements"), update scoped_guard() formatting.
> Also, see the related fix [1].
>
> Cc: Günther Noack <gnoack@google.com>
> Cc: Miguel Ojeda <ojeda@kernel.org>
> Link: https://lore.kernel.org/r/20260708105713.2073335-1-mic@digikod.net [1]
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> ---
> security/landlock/task.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/security/landlock/task.c b/security/landlock/task.c
> index 7ddf211f75c3..360d226d0f51 100644
> --- a/security/landlock/task.c
> +++ b/security/landlock/task.c
> @@ -95,8 +95,7 @@ static int hook_ptrace_access_check(struct task_struct *const child,
> if (!parent_subject)
> return 0;
>
> - scoped_guard(rcu)
> - {
> + scoped_guard(rcu) {
> const struct landlock_ruleset *const child_dom =
> landlock_get_task_domain(child);
> err = domain_ptrace(parent_subject->domain, child_dom);
> @@ -370,8 +369,7 @@ static int hook_task_kill(struct task_struct *const p,
> if (!subject)
> return 0;
>
> - scoped_guard(rcu)
> - {
> + scoped_guard(rcu) {
> is_scoped = domain_is_scoped(subject->domain,
> landlock_get_task_domain(p),
> signal_scope.scope);
> @@ -422,8 +420,7 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
> if (task_tgid(tsk) == landlock_file(fown->file)->fown_tg)
> return 0;
>
> - scoped_guard(rcu)
> - {
> + scoped_guard(rcu) {
> is_scoped = domain_is_scoped(subject->domain,
> landlock_get_task_domain(tsk),
> signal_scope.scope);
> --
> 2.54.0
Reviewed-by: Günther Noack <gnoack@google.com>
^ permalink raw reply
* [PATCH 3/3] landlock: Document LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
From: Justin Suess @ 2026-07-08 13:39 UTC (permalink / raw)
To: mic, linux-security-module; +Cc: gnoack, Justin Suess
In-Reply-To: <20260708133928.852999-1-utilityemal77@gmail.com>
Document staged no_new_privs on exec, following the same compatibility
section style as previous ABI additions.
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---
Documentation/userspace-api/landlock.rst | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 5a63d4476c1c..1d779dd7bb5f 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -8,7 +8,7 @@ Landlock: unprivileged access control
=====================================
:Author: Mickaël Salaün
-:Date: June 2026
+:Date: July 2026
The goal of Landlock is to enable restriction of ambient rights (e.g. global
filesystem or network access) for a set of processes. Because Landlock
@@ -789,6 +789,25 @@ when at least one sys_landlock_add_rule() call is made for it with the
``LANDLOCK_ADD_RULE_QUIET`` flag, additional add-rule calls for the same
object without this flag do not clear it.
+Staged no_new_privs on exec (ABI < 11)
+--------------------------------------
+
+Starting with the Landlock ABI version 11, it is possible to stage
+no_new_privs so that it is only set at the next :manpage:`execve(2)` of the
+calling thread, past its point of no return, using the
+``LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC`` flag passed to
+sys_landlock_restrict_self(). This flag may be used with a ``ruleset_fd``
+value of -1 to stage no_new_privs without enforcing a ruleset, and does not
+relax the no_new_privs / ``CAP_SYS_ADMIN`` requirement of the system call.
+This flag does not change how the next :manpage:`execve(2)` itself computes
+credentials: set-user-ID, set-group-ID and file capabilities are still
+honored for that execution. The executed program then runs with
+no_new_privs set, with its usual effect on subsequent :manpage:`execve(2)`
+calls. Staging is per-thread by default: when combined with
+``LANDLOCK_RESTRICT_SELF_TSYNC``, the staged no_new_privs is propagated to
+the sibling threads along with the rest of the Landlock configuration, and
+each thread then sets no_new_privs at its own next :manpage:`execve(2)`.
+
.. _kernel_support:
Kernel support
--
2.54.0
^ permalink raw reply related
* [PATCH 2/3] selftests/landlock: Test LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
From: Justin Suess @ 2026-07-08 13:39 UTC (permalink / raw)
To: mic, linux-security-module; +Cc: gnoack, Justin Suess
In-Reply-To: <20260708133928.852999-1-utilityemal77@gmail.com>
Add an nnp_on_exec fixture checking that staging no_new_privs does not
set it before execve(2) but does set it for the executed program, with
and without a ruleset, and that LANDLOCK_RESTRICT_SELF_TSYNC propagates
the staged state to sibling threads. Also check that the
no_new_privs/CAP_SYS_ADMIN requirement still applies to stage-only
calls.
Update the ABI version and last-flag checks accordingly.
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---
tools/testing/selftests/landlock/base_test.c | 259 ++++++++++++++++++-
1 file changed, 255 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index cbd3c1669951..55ae26a72752 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -11,9 +11,12 @@
#include <fcntl.h>
#include <linux/keyctl.h>
#include <linux/landlock.h>
+#include <pthread.h>
+#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/socket.h>
+#include <sys/stat.h>
#include <sys/types.h>
#include "common.h"
@@ -76,7 +79,7 @@ TEST(abi_version)
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
};
- ASSERT_EQ(10, landlock_create_ruleset(NULL, 0,
+ ASSERT_EQ(11, landlock_create_ruleset(NULL, 0,
LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
@@ -288,7 +291,7 @@ TEST(restrict_self_fd)
EXPECT_EQ(EBADFD, errno);
}
-TEST(restrict_self_fd_logging_flags)
+TEST(restrict_self_fd_flags)
{
int fd;
@@ -302,11 +305,16 @@ TEST(restrict_self_fd_logging_flags)
EXPECT_EQ(-1, landlock_restrict_self(
fd, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
EXPECT_EQ(EBADFD, errno);
+
+ /* Same for LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC. */
+ EXPECT_EQ(-1, landlock_restrict_self(
+ fd, LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC));
+ EXPECT_EQ(EBADFD, errno);
}
-TEST(restrict_self_logging_flags)
+TEST(restrict_self_flags)
{
- const __u32 last_flag = LANDLOCK_RESTRICT_SELF_TSYNC;
+ const __u32 last_flag = LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC;
/* Tests invalid flag combinations. */
@@ -349,6 +357,12 @@ TEST(restrict_self_logging_flags)
LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON));
EXPECT_EQ(EBADF, errno);
+ EXPECT_EQ(-1,
+ landlock_restrict_self(
+ -1, LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF |
+ LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC));
+ EXPECT_EQ(EBADF, errno);
+
/* Tests with an invalid ruleset_fd. */
EXPECT_EQ(-1, landlock_restrict_self(
@@ -359,6 +373,243 @@ TEST(restrict_self_logging_flags)
-1, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
}
+/*
+ * Exits with the NoNewPrivs value of the executed shell, as read from
+ * /proc/self/status, making the staged no_new_privs observable after an
+ * execve(2).
+ */
+static const char nnp_script[] =
+ "#!/bin/sh\n"
+ "while read -r label value; do\n"
+ " if [ \"$label\" = \"NoNewPrivs:\" ]; then\n"
+ " exit \"$value\"\n"
+ " fi\n"
+ "done < /proc/self/status\n"
+ "exit 42\n";
+
+/* Returns the no_new_privs value inherited through fork(2) and execve(2). */
+static int get_nnp_after_exec(const char *const script_path)
+{
+ int status;
+ const pid_t child = fork();
+
+ if (child < 0)
+ return -errno;
+
+ if (child == 0) {
+ char *const argv[] = { (char *)script_path, NULL };
+
+ execve(script_path, argv, NULL);
+ _exit(127);
+ }
+
+ if (waitpid(child, &status, 0) != child)
+ return -ECHILD;
+
+ if (!WIFEXITED(status))
+ return -EIO;
+
+ return WEXITSTATUS(status);
+}
+
+struct nnp_staging_thread {
+ const char *script_path;
+ int ruleset_fd;
+ __u32 flags;
+ int restrict_ret;
+ int restrict_errno;
+ int open_write_ret;
+ int open_write_errno;
+ int nnp_before_exec;
+ int nnp_after_exec;
+};
+
+/*
+ * Stages no_new_privs from a sibling thread of the test thread, so that the
+ * test thread can observe whether LANDLOCK_RESTRICT_SELF_TSYNC propagated the
+ * staged state.
+ */
+static void *stage_nnp_on_exec(void *data)
+{
+ struct nnp_staging_thread *const ctx = data;
+
+ ctx->restrict_ret = landlock_restrict_self(ctx->ruleset_fd, ctx->flags);
+ ctx->restrict_errno = errno;
+
+ /*
+ * Tries to open the script for writing to check that a ruleset passed
+ * along LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC is enforced immediately,
+ * unlike the staged no_new_privs.
+ */
+ ctx->open_write_ret = open(ctx->script_path, O_WRONLY | O_CLOEXEC);
+ ctx->open_write_errno = errno;
+ if (ctx->open_write_ret >= 0)
+ close(ctx->open_write_ret);
+
+ ctx->nnp_before_exec = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
+ ctx->nnp_after_exec = get_nnp_after_exec(ctx->script_path);
+ return NULL;
+}
+
+FIXTURE(nnp_on_exec)
+{
+ char script_path[sizeof("/tmp/landlock_nnp_XXXXXX")];
+};
+
+FIXTURE_VARIANT(nnp_on_exec)
+{
+ const bool with_ruleset;
+ const bool tsync;
+ const bool nnp_before;
+ const bool cap_sys_admin;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, no_ruleset) {
+ /* clang-format on */
+ .cap_sys_admin = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, with_ruleset) {
+ /* clang-format on */
+ .with_ruleset = true,
+ .cap_sys_admin = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, no_ruleset_tsync) {
+ /* clang-format on */
+ .tsync = true,
+ .cap_sys_admin = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, with_ruleset_tsync) {
+ /* clang-format on */
+ .with_ruleset = true,
+ .tsync = true,
+ .cap_sys_admin = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, nnp_already_set) {
+ /* clang-format on */
+ .nnp_before = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, nnp_already_set_tsync) {
+ /* clang-format on */
+ .nnp_before = true,
+ .tsync = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, unprivileged) {
+ /* clang-format on */
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(nnp_on_exec, unprivileged_tsync) {
+ /* clang-format on */
+ .tsync = true,
+};
+
+FIXTURE_SETUP(nnp_on_exec)
+{
+ int script_fd;
+
+ disable_caps(_metadata);
+
+ memcpy(self->script_path, "/tmp/landlock_nnp_XXXXXX",
+ sizeof(self->script_path));
+ script_fd = mkstemp(self->script_path);
+ ASSERT_LE(0, script_fd);
+ ASSERT_EQ(sizeof(nnp_script) - 1,
+ write(script_fd, nnp_script, sizeof(nnp_script) - 1));
+ ASSERT_EQ(0, fchmod(script_fd, 0700));
+ ASSERT_EQ(0, close(script_fd));
+}
+
+FIXTURE_TEARDOWN(nnp_on_exec)
+{
+ EXPECT_EQ(0, unlink(self->script_path));
+}
+
+TEST_F(nnp_on_exec, staging)
+{
+ /* The nnp/CAP_SYS_ADMIN gate applies even to stage-only calls. */
+ const bool expect_success = variant->nnp_before ||
+ variant->cap_sys_admin;
+ struct nnp_staging_thread staging = {
+ .script_path = self->script_path,
+ .ruleset_fd = -1,
+ .flags = LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC,
+ };
+ pthread_t thread;
+
+ if (variant->tsync)
+ staging.flags |= LANDLOCK_RESTRICT_SELF_TSYNC;
+
+ if (variant->with_ruleset) {
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_fs = LANDLOCK_ACCESS_FS_WRITE_FILE,
+ };
+
+ staging.ruleset_fd =
+ landlock_create_ruleset(&ruleset_attr,
+ sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, staging.ruleset_fd);
+ }
+
+ if (variant->nnp_before)
+ ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+ if (variant->cap_sys_admin)
+ set_cap(_metadata, CAP_SYS_ADMIN);
+
+ /* The staging thread inherits no_new_privs and capabilities. */
+ ASSERT_EQ(0, pthread_create(&thread, NULL, stage_nnp_on_exec,
+ &staging));
+ ASSERT_EQ(0, pthread_join(thread, NULL));
+
+ if (variant->cap_sys_admin)
+ clear_cap(_metadata, CAP_SYS_ADMIN);
+
+ if (expect_success) {
+ EXPECT_EQ(0, staging.restrict_ret);
+ } else {
+ EXPECT_EQ(-1, staging.restrict_ret);
+ EXPECT_EQ(EPERM, staging.restrict_errno);
+ }
+
+ /* A ruleset is enforced immediately, unlike the staged no_new_privs. */
+ if (variant->with_ruleset) {
+ EXPECT_EQ(-1, staging.open_write_ret);
+ EXPECT_EQ(EACCES, staging.open_write_errno);
+ } else {
+ EXPECT_LE(0, staging.open_write_ret);
+ }
+
+ /* Staging never sets no_new_privs before the execve(2)... */
+ EXPECT_EQ(variant->nnp_before, staging.nnp_before_exec);
+ /* ...but a successful call sets it for the executed program. */
+ EXPECT_EQ(expect_success, staging.nnp_after_exec);
+
+ /*
+ * On this sibling thread, the staged state is only visible if it was
+ * propagated with LANDLOCK_RESTRICT_SELF_TSYNC, and it is still not
+ * set before the execve(2).
+ */
+ EXPECT_EQ(variant->nnp_before,
+ prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+ EXPECT_EQ((variant->nnp_before || (expect_success && variant->tsync)),
+ get_nnp_after_exec(self->script_path));
+
+ if (variant->with_ruleset)
+ EXPECT_EQ(0, close(staging.ruleset_fd));
+}
+
TEST(ruleset_fd_io)
{
struct landlock_ruleset_attr ruleset_attr = {
--
2.54.0
^ permalink raw reply related
* [PATCH 1/3] landlock: Add LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
From: Justin Suess @ 2026-07-08 13:39 UTC (permalink / raw)
To: mic, linux-security-module; +Cc: gnoack, Justin Suess
In-Reply-To: <20260708133928.852999-1-utilityemal77@gmail.com>
Add a landlock_restrict_self(2) flag to stage no_new_privs so that it is
only set at the next execve(2) of the calling thread, past its point of
no return. This makes it possible to prepare an execution environment
where the new program runs with no_new_privs, without changing the
behavior of the calling program, and without leaving no_new_privs set if
the execve(2) fails.
The staged bit lives in the Landlock credential blob and is installed by
a new bprm_committing_creds hook. This flag does not relax the
no_new_privs/CAP_SYS_ADMIN requirement of landlock_restrict_self(2), and
may be used with a ruleset_fd of -1 to stage no_new_privs without
enforcing a ruleset. Combined with LANDLOCK_RESTRICT_SELF_TSYNC, the
staged state is propagated to sibling threads like the rest of the
Landlock credential state, and each thread then sets no_new_privs at its
own next execve(2).
Because no_new_privs is only set once the credentials of the new program
have been computed, this flag does not change how the next execve(2)
itself computes credentials: set-user-ID, set-group-ID and file
capabilities are still honored for that execution. The executed program
then runs with no_new_privs set, with its usual effect on subsequent
execve(2) calls.
Bump the Landlock ABI version to 11.
Cc: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---
include/uapi/linux/landlock.h | 36 ++++++++++++++++++++++-
security/landlock/cred.c | 22 ++++++++++++++
security/landlock/cred.h | 8 ++++++
security/landlock/limits.h | 2 +-
security/landlock/syscalls.c | 54 ++++++++++++++++++++++++++---------
5 files changed, 107 insertions(+), 15 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 7ffe2ef127ee..8d5b41d94c4a 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -190,13 +190,47 @@ struct landlock_ruleset_attr {
* logging configurations on these threads.
*
* If the calling thread is running with no_new_privs, this operation
- * enables no_new_privs on the sibling threads as well.
+ * enables no_new_privs on the sibling threads as well. If the calling
+ * thread has no_new_privs staged with
+ * %LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC (whether by the same call or a
+ * previous one), the staged state is propagated to the sibling threads as
+ * well.
+ *
+ * The following flag stages no_new_privs so that it only takes effect at the
+ * next :manpage:`execve(2)` of the calling thread, rather than immediately.
+ * It does not relax the permission check performed by
+ * sys_landlock_restrict_self(): the calling thread must still be running with
+ * no_new_privs or hold %CAP_SYS_ADMIN in its namespace.
+ *
+ * %LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
+ * Sets the no_new_privs attribute of the calling thread, but only at the
+ * next :manpage:`execve(2)` and past its point of no return, so a failed
+ * :manpage:`execve(2)` leaves the attribute unchanged. Because
+ * sys_landlock_restrict_self() already requires no_new_privs or
+ * %CAP_SYS_ADMIN, this flag cannot be used to defer around that
+ * requirement: when no_new_privs is already set it is effectively a
+ * no-op, and otherwise the caller must hold %CAP_SYS_ADMIN. This flag
+ * may be used with a @ruleset_fd value of -1 to stage no_new_privs
+ * without enforcing a ruleset.
+ *
+ * This flag does not change how the next :manpage:`execve(2)` itself
+ * computes credentials: set-user-ID, set-group-ID and file capabilities
+ * are still honored for that execution. The executed program then runs
+ * with no_new_privs set, with its usual effect on subsequent
+ * :manpage:`execve(2)` calls.
+ *
+ * Staging is per-thread by default. When combined with
+ * %LANDLOCK_RESTRICT_SELF_TSYNC, the staged no_new_privs is propagated
+ * to the sibling threads along with the rest of the Landlock
+ * configuration, and each thread then sets no_new_privs at its own next
+ * :manpage:`execve(2)`.
*/
/* clang-format off */
#define LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF (1U << 0)
#define LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON (1U << 1)
#define LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF (1U << 2)
#define LANDLOCK_RESTRICT_SELF_TSYNC (1U << 3)
+#define LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC (1U << 4)
/* clang-format on */
/**
diff --git a/security/landlock/cred.c b/security/landlock/cred.c
index cc419de75cd6..31fa4f78adef 100644
--- a/security/landlock/cred.c
+++ b/security/landlock/cred.c
@@ -10,6 +10,7 @@
#include <linux/binfmts.h>
#include <linux/cred.h>
#include <linux/lsm_hooks.h>
+#include <linux/sched.h>
#include "common.h"
#include "cred.h"
@@ -52,11 +53,32 @@ static int hook_bprm_creds_for_exec(struct linux_binprm *const bprm)
#endif /* CONFIG_AUDIT */
+/*
+ * Installs the no_new_privs attribute staged with
+ * LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC.
+ *
+ * This hook runs from begin_new_exec(), past the execution's point of no
+ * return: a binary that cannot be loaded (or any earlier failure) never reaches
+ * this point, so a failed execve(2) leaves the thread's no_new_privs attribute
+ * untouched.
+ */
+static void hook_bprm_committing_creds(const struct linux_binprm *const bprm)
+{
+ struct landlock_cred_security *const llcred = landlock_cred(bprm->cred);
+
+ if (llcred->set_nnp_on_exec) {
+ task_set_no_new_privs(current);
+ llcred->set_nnp_on_exec = 0;
+ }
+}
+
static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(cred_prepare, hook_cred_prepare),
LSM_HOOK_INIT(cred_transfer, hook_cred_transfer),
LSM_HOOK_INIT(cred_free, hook_cred_free),
+ LSM_HOOK_INIT(bprm_committing_creds, hook_bprm_committing_creds),
+
#ifdef CONFIG_AUDIT
LSM_HOOK_INIT(bprm_creds_for_exec, hook_bprm_creds_for_exec),
#endif /* CONFIG_AUDIT */
diff --git a/security/landlock/cred.h b/security/landlock/cred.h
index f287c56b5fd4..673206d3c3f3 100644
--- a/security/landlock/cred.h
+++ b/security/landlock/cred.h
@@ -35,6 +35,14 @@ struct landlock_cred_security {
*/
struct landlock_ruleset *domain;
+ /**
+ * @set_nnp_on_exec: Set if %LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
+ * requested that no_new_privs be enabled at the next execve(2).
+ * Propagated to sibling threads by %LANDLOCK_RESTRICT_SELF_TSYNC like
+ * the rest of this struct. Consumed by hook_bprm_committing_creds().
+ */
+ u8 set_nnp_on_exec : 1;
+
#ifdef CONFIG_AUDIT
/**
* @domain_exec: Bitmask identifying the domain layers that were enforced by
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 08d5f2f6d321..29c190d00540 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -34,7 +34,7 @@
#define LANDLOCK_NUM_ACCESS_MAX \
MAX(MAX(LANDLOCK_NUM_ACCESS_FS, LANDLOCK_NUM_ACCESS_NET), LANDLOCK_NUM_SCOPE)
-#define LANDLOCK_LAST_RESTRICT_SELF LANDLOCK_RESTRICT_SELF_TSYNC
+#define LANDLOCK_LAST_RESTRICT_SELF LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
#define LANDLOCK_MASK_RESTRICT_SELF ((LANDLOCK_LAST_RESTRICT_SELF << 1) - 1)
/* clang-format on */
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 36b02892c62f..daed1ea80455 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -169,7 +169,7 @@ static const struct file_operations ruleset_fops = {
* If the change involves a fix that requires userspace awareness, also update
* the errata documentation in Documentation/userspace-api/landlock.rst .
*/
-const int landlock_abi_version = 10;
+const int landlock_abi_version = 11;
/**
* sys_landlock_create_ruleset - Create a new ruleset
@@ -502,12 +502,21 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
* - %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON
* - %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF
* - %LANDLOCK_RESTRICT_SELF_TSYNC
+ * - %LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
*
* This system call enforces a Landlock ruleset on the current thread.
* Enforcing a ruleset requires that the task has %CAP_SYS_ADMIN in its
* namespace or is running with no_new_privs. This avoids scenarios where
* unprivileged tasks can affect the behavior of privileged children.
*
+ * With %LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC, no_new_privs is not set
+ * immediately but staged to be set at the next execve(2), past its point of no
+ * return. This flag does not relax the no_new_privs / %CAP_SYS_ADMIN
+ * requirement above. Staging is per-thread by default; when combined with
+ * %LANDLOCK_RESTRICT_SELF_TSYNC, the staged no_new_privs is propagated to the
+ * sibling threads along with the rest of the Landlock credential state, and
+ * each thread then sets no_new_privs at its own next execve(2).
+ *
* Return: 0 on success, or -errno on failure. Possible returned errors are:
*
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
@@ -526,6 +535,10 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
flags)
{
+ /* Flags that do not require a ruleset_fd. */
+ const __u32 fd_optional_flags =
+ LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF |
+ LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC;
struct landlock_ruleset *ruleset __free(landlock_put_ruleset) = NULL;
struct cred *new_cred;
struct landlock_cred_security *new_llcred;
@@ -538,6 +551,10 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
/*
* Similar checks as for seccomp(2), except that an -EPERM may be
* returned.
+ *
+ * This gate runs before any flag-specific handling, so
+ * LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC cannot be used to defer around the
+ * no_new_privs / CAP_SYS_ADMIN requirement.
*/
if (!task_no_new_privs(current) &&
!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
@@ -555,14 +572,15 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
log_subdomains = !(flags & LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF);
/*
- * It is allowed to set LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF with
- * -1 as ruleset_fd, optionally combined with
- * LANDLOCK_RESTRICT_SELF_TSYNC to propagate this configuration to all
- * threads. No other flag must be set.
+ * A ruleset is not required when only muting subdomain logs
+ * (LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF, optionally combined with
+ * LANDLOCK_RESTRICT_SELF_TSYNC to propagate it to all threads) and/or
+ * staging no_new_privs on exec (LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC).
+ * Such calls may pass -1 as ruleset_fd. Any other flag (or the absence
+ * of these) requires a real ruleset.
*/
- if (!(ruleset_fd == -1 &&
- (flags & ~LANDLOCK_RESTRICT_SELF_TSYNC) ==
- LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF)) {
+ if (!(ruleset_fd == -1 && (flags & fd_optional_flags) &&
+ !(flags & ~(fd_optional_flags | LANDLOCK_RESTRICT_SELF_TSYNC)))) {
/* Gets and checks the ruleset. */
ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
if (IS_ERR(ruleset))
@@ -583,11 +601,12 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
#endif /* CONFIG_AUDIT */
/*
- * The only case when a ruleset may not be set is if
- * LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF is set (optionally with
- * LANDLOCK_RESTRICT_SELF_TSYNC) and ruleset_fd is -1. We could
- * optimize this case by not calling commit_creds() if this flag was
- * already set, but it is not worth the complexity.
+ * A ruleset may legitimately be absent here when only muting subdomain
+ * logs (LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF, optionally with
+ * LANDLOCK_RESTRICT_SELF_TSYNC) and/or staging no_new_privs on exec
+ * (LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC) with ruleset_fd == -1. We could
+ * optimize some of these cases by not calling commit_creds(), but it is
+ * not worth the complexity.
*/
if (ruleset) {
/*
@@ -618,6 +637,15 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
#endif /* CONFIG_AUDIT */
}
+ /*
+ * Stages no_new_privs to be set at the next execve(2). Because the bit
+ * lives in new_cred, TSYNC below propagates it to the sibling threads
+ * (whether it was staged by this call or a previous one), and each
+ * thread then sets no_new_privs at its own next execve(2).
+ */
+ if (flags & LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC)
+ new_llcred->set_nnp_on_exec = 1;
+
if (flags & LANDLOCK_RESTRICT_SELF_TSYNC) {
const int err = landlock_restrict_sibling_threads(
current_cred(), new_cred);
--
2.54.0
^ permalink raw reply related
* [PATCH 0/3] Implement LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
From: Justin Suess @ 2026-07-08 13:39 UTC (permalink / raw)
To: mic, linux-security-module; +Cc: gnoack, Justin Suess
Good morning,
This series adds a new landlock_restrict_self(2) flag:
LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC.
This flag stages a bit in the Landlock credentials indicating that the
next successful execution will set the no_new_privs attribute while
committing its new credentials.
Differences from prctl(PR_SET_NO_NEW_PRIVS):
PR_SET_NO_NEW_PRIVS takes effect immediately: it prevents gaining
privileges through set-user-ID, set-group-ID and file capabilities
starting with the very next execve(2).
LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC instead only sets the task's
no_new_privs attribute once the next execve(2) is guaranteed to succeed
(past its point of no return, in bprm_committing_creds), after any
privilege gain through set-user-ID, set-group-ID or file capabilities
has already taken place. The executed program then runs with
no_new_privs, so subsequent executions cannot gain privileges. A
failed execve(2) leaves no_new_privs untouched.
Use cases:
Enforcing a Landlock ruleset requires that the calling process either
already has no_new_privs set or possesses CAP_SYS_ADMIN. This series
does not grant any exception to this rule; for a caller that already
has no_new_privs set, the flag is effectively a no-op. It is therefore
mostly useful for CAP_SYS_ADMIN callers that need to execute programs
that legitimately escalate privileges (e.g. transition to another
user), while ensuring that further executions cannot gain privileges.
Consider a sandbox launcher that depends on a set-user-ID helper, such
as launching applications through bubblewrap on distributions where
unprivileged user namespaces are disabled and bwrap is installed
set-user-ID root. The launcher cannot set PR_SET_NO_NEW_PRIVS before
the execution, as that would neuter the very helper it depends on:
sandbox launcher (CAP_SYS_ADMIN)
|
| landlock_restrict_self(-1, LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC)
V
/usr/bin/bwrap (set-user-ID root: honored for this execution;
| no_new_privs set once the execution is past its
| point of no return)
V
sandboxed application (runs with no_new_privs; cannot gain
privileges through any further execution, and
may enforce its own Landlock ruleset without
CAP_SYS_ADMIN)
This flag also closes a gap for CAP_SYS_ADMIN callers of
landlock_restrict_self(2) itself. The no_new_privs/CAP_SYS_ADMIN
requirement exists to keep set-user-ID programs from running confused
inside a sandbox they do not expect. However, a privileged process
that enforces a domain without setting no_new_privs leaves that hole
open for all of its descendants: anything running in the domain may
still execute a set-user-ID binary, which then runs privileged under a
restricted view of the system. A privileged process that needs one
legitimate set-user-ID/set-group-ID transition currently has to choose
between breaking that transition (setting no_new_privs first) or
leaving the hole open for the lifetime of the domain.
LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC allows the one intended transition
and then closes the hole.
Design:
This flag is implemented simply: a bit is stored in the Landlock
credential blob (struct landlock_cred_security) indicating whether the
next execution should set no_new_privs when it commits its new
credentials.
The bit is not coupled to any ruleset and, like
LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF, may be passed with no
ruleset (i.e. ruleset_fd = -1). It may also be combined with
LANDLOCK_RESTRICT_SELF_TSYNC to propagate the staged state to sibling
threads, each thread then setting no_new_privs at its own next
execve(2).
The staged bit is inherited across fork(2) and persists in the
credentials until the next successful execution. To consume it,
Landlock handles the bprm_committing_creds hook, which runs while the
credentials of the new program are being committed: if the bit is set,
task_set_no_new_privs(current) is called and the bit is cleared.
Again, this flag does not bypass the requirement to either have
CAP_SYS_ADMIN or no_new_privs already set to call
landlock_restrict_self(2).
The Landlock ABI version is bumped to 11.
Test coverage:
The new nnp_on_exec fixture generates a shell script that reads the
NoNewPrivs value from /proc/self/status and exits with it. The
variants select the conditions under which the flag is tested (with
and without a ruleset, with and without CAP_SYS_ADMIN/no_new_privs
already set, with and without TSYNC, etc.), then compare no_new_privs
before the execution and in the executed script. The ruleset variants
also check that a ruleset passed along the flag is enforced
immediately, unlike the staged no_new_privs.
Justin Suess (3):
landlock: Add LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
selftests/landlock: Test LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
landlock: Document LANDLOCK_RESTRICT_SELF_NNP_ON_EXEC
Documentation/userspace-api/landlock.rst | 21 +-
include/uapi/linux/landlock.h | 36 ++-
security/landlock/cred.c | 22 ++
security/landlock/cred.h | 8 +
security/landlock/limits.h | 2 +-
security/landlock/syscalls.c | 54 +++-
tools/testing/selftests/landlock/base_test.c | 259 ++++++++++++++++++-
7 files changed, 382 insertions(+), 20 deletions(-)
--
2.54.0
^ permalink raw reply
* Re: [PATCH v5 bpf-next 0/3] bpf: add bpf_init_inode_xattr kfunc for atomic inode labeling
From: David Windsor @ 2026-07-08 12:51 UTC (permalink / raw)
To: Kumar Kartikeya Dwivedi
Cc: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Jiri Olsa, Emil Tsalapatis,
Matt Bobrowski, Paul Moore, James Morris, Serge E . Hallyn,
Casey Schaufler, Stephen Smalley, Ondrej Mosnacek, Mimi Zohar,
Roberto Sassu, Dmitry Kasatkin, Eric Snowberg, Alexander Viro,
Christian Brauner, Jan Kara, Shuah Khan, bpf,
linux-security-module, linux-fsdevel, linux-integrity, selinux,
linux-kselftest, linux-kernel
In-Reply-To: <DJSV0P2OINKE.34OCOC34KFEEF@gmail.com>
On Tue, Jul 7, 2026 at 11:12 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> On Wed Jul 8, 2026 at 2:09 AM CEST, David Windsor wrote:
> > Many in-kernel LSMs (SELinux, Smack, IMA) store security labels in
> > extended attributes. For these LSMs, atomic labeling during inode
> > creation is critical: if the inode becomes accessible before its xattr
> > is set, it is briefly unlabeled, which can disrupt LSMs making policy
> > decisions based on file labels.
> >
> > Existing LSMs solve this by setting xattrs directly in the
> > inode_init_security hook, which runs before the inode becomes
> > accessible. BPF LSM programs currently lack this capability because
> > the hook uses an output parameter (xattr_count) that BPF programs
> > cannot write to, and existing kfuncs like bpf_set_dentry_xattr
> > require a dentry that isn't available until after the inode is
> > accessible.
> >
> > This series introduces the bpf_init_inode_xattr() kfunc, which takes
> > the combined inode_init_security xattr context argument and claims a
> > slot in it via the new security_lsmxattr_add() LSM helper.
> >
>
> There are various CI failures in newly added tests, I don't think any of them
> are passing. Please fix before respinning.
>
> https://github.com/kernel-patches/bpf/pull/12730
>
> E.g. both test_init_inode_xattr and test_init_inode_xattr_slot do not have
> expected results.
>
This is happening because the path "/tmp" in bpf ci isn't mounted on
tmpfs, rather on 9p:
[ 5.813072] VFS: Mounted root (9p filesystem) on device 0:22.
[ 5.924390] vmtest: Mounting tmpfs at /dev/shm
[ 5.971012] vmtest: Mounting tmpfs at /run
[ 6.096271] vmtest: Mounting tmpfs at /mnt
... which doesn't call inode_init_security. Changing the test to
create its file in /dev/shm, which has a real tmpfs, fixes this. We
can update the test to skip on filesystems where the hook doesn't
fire.
I'll wait to gather feedback from Alexei and Paul before sending v6.
> pw-bot: cr
>
> > [...]
^ permalink raw reply
* [RFC/discuss] memfd_secret(): opt-in visibility for security monitoring (eBPF/audit)
From: BoxStrikesTeam @ 2026-07-08 12:09 UTC (permalink / raw)
To: rppt@kernel.org, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-security-module@vger.kernel.org,
paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com
Hi,
While experimenting with mseal() and memfd_secret() together on a
recent kernel, I ran into what looks like a gap worth discussing:
content placed in memfd_secret()-backed memory is invisible not just
to other processes, but also to in-kernel tracing/observability
mechanisms such as eBPF's bpf_probe_read_user() (EFAULT, as expected,
since the region is removed from the direct map and kernel page
tables entirely).
That's working as designed for the threat model memfd_secret targets
(protect secrets even from a compromised kernel / ROP-based
exfiltration). But it does mean a local, unprivileged process can
now allocate memory that:
1. Is invisible to kernel-side introspection (eBPF tracing,
/proc/<pid>/mem, ptrace-based tooling) once populated via
memfd_secret(), and
2. Can additionally be sealed against mprotect()/munmap()/mremap()
via mseal() so its protection bits can't be relaxed either.
Neither primitive alone is new or alarming - mseal() protects mapping
metadata, not confidentiality, and memfd_secret() is explicitly
opt-in and disabled by default. But combined, they let a process
carve out a region that a host-based EDR relying on eBPF
tracing/probe_read helpers cannot inspect, and cannot force back into
an inspectable state either. For userland security tooling that
assumes 'anything a tracing eBPF program can attach to, it can read',
this is a small blind spot.
I want to be clear I'm not suggesting memfd_secret()'s core guarantee
should be weakened - the ability to keep data hidden from a
compromised kernel is the entire point, and forcibly exposing content
to tracing programs would undermine that model and create a new
attack surface via the eBPF verifier/helper path itself.
What I'd like to raise for discussion instead is something closer to
what was already anticipated in the original series - Mike, your
commit message for memfd_secret() mentions: 'Once there will be a use
case that will require exposing secretmem to the kernel it will be an
opt-in request in the system call flags.' Two lighter-weight
directions that stay consistent with that opt-in philosophy:
a) An LSM hook / audit event at memfd_secret() call time (this
echoes Christian Gottsche's 2022 RFC to label secretmem inodes
via inode_init_security_anon for SELinux). Even without content
visibility, logging 'process X created a N-byte kernel-invisible
mapping' gives EDR/audit systems a behavioral signal to alert on,
without touching the confidentiality guarantee at all.
b) A distinct opt-in flag (as foreshadowed in the original commit)
that a process could set to allow a CAP_BPF/CAP_SYS_ADMIN-gated
tracing context to read the region for legitimate
monitoring/debugging - fully opt-in, off by default, and never
implicitly available to unprivileged tracers.
Is (a) something that's been considered further since the 2022
secretmem-inode-labeling thread? And is there any existing tracking
issue for the kind of opt-in-visibility idea in (b), or was it
dropped as not worth the complexity?
Happy to help test/write a small selftest if there's interest in
pursuing either direction.
Thanks,
BoxStrike Team.
Researcher:Eneshan Erdoğan Karaca, Other ananymous
Researcher emails:cyberblackk@proton.me
^ permalink raw reply
* [PATCH v1] landlock: Update formatting
From: Mickaël Salaün @ 2026-07-08 11:06 UTC (permalink / raw)
To: Günther Noack
Cc: Mickaël Salaün, linux-security-module, Bart Van Assche,
Miguel Ojeda
Following commit 99df2a8eba34 ("clang-format: fix formatting of guard()
and scoped_guard() statements"), update scoped_guard() formatting.
Also, see the related fix [1].
Cc: Günther Noack <gnoack@google.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20260708105713.2073335-1-mic@digikod.net [1]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
security/landlock/task.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/security/landlock/task.c b/security/landlock/task.c
index 7ddf211f75c3..360d226d0f51 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -95,8 +95,7 @@ static int hook_ptrace_access_check(struct task_struct *const child,
if (!parent_subject)
return 0;
- scoped_guard(rcu)
- {
+ scoped_guard(rcu) {
const struct landlock_ruleset *const child_dom =
landlock_get_task_domain(child);
err = domain_ptrace(parent_subject->domain, child_dom);
@@ -370,8 +369,7 @@ static int hook_task_kill(struct task_struct *const p,
if (!subject)
return 0;
- scoped_guard(rcu)
- {
+ scoped_guard(rcu) {
is_scoped = domain_is_scoped(subject->domain,
landlock_get_task_domain(p),
signal_scope.scope);
@@ -422,8 +420,7 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
if (task_tgid(tsk) == landlock_file(fown->file)->fown_tg)
return 0;
- scoped_guard(rcu)
- {
+ scoped_guard(rcu) {
is_scoped = domain_is_scoped(subject->domain,
landlock_get_task_domain(tsk),
signal_scope.scope);
--
2.54.0
^ permalink raw reply related
* Re: [PATCH v2] selftests/landlock: fix spelling error in fs_test comment
From: Mickaël Salaün @ 2026-07-08 10:42 UTC (permalink / raw)
To: Wang Yan
Cc: gnoack, shuah, linux-security-module, linux-kselftest,
linux-kernel
In-Reply-To: <20260702015823.368529-1-wangyan01@kylinos.cn>
Applied, thanks!
On Thu, Jul 02, 2026 at 09:58:23AM +0800, Wang Yan wrote:
> Fix typo "allowes" -> "allows" in Landlock filesystem test comment.
>
> Signed-off-by: Wang Yan <wangyan01@kylinos.cn>
> ---
> tools/testing/selftests/landlock/fs_test.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
> index 86e08aa6e0a7..e672089e9329 100644
> --- a/tools/testing/selftests/landlock/fs_test.c
> +++ b/tools/testing/selftests/landlock/fs_test.c
> @@ -6927,7 +6927,7 @@ TEST_F_FORK(layout2_overlay, same_content_different_file)
> ASSERT_EQ(0, test_open(path_entry, O_RDWR));
> }
>
> - /* Only allowes access to the merge hierarchy. */
> + /* Only allows access to the merge hierarchy. */
> enforce_fs(_metadata, ACCESS_RW, layer5_merge_only);
>
> /* Checks new accesses on lower layer. */
> --
> 2.25.1
>
>
^ permalink raw reply
* Re: [PATCH] landlock: Documentation wording cleanups
From: Mickaël Salaün @ 2026-07-08 10:40 UTC (permalink / raw)
To: Günther Noack
Cc: linux-doc, linux-security-module, Alejandro Colomar,
Alejandro Colomar
In-Reply-To: <20260516190112.4924-1-gnoack3000@gmail.com>
Thanks, applied!
On Sat, May 16, 2026 at 09:01:12PM +0200, Günther Noack wrote:
> Documentation cleanups suggested by Alejandro Colomar,
> which we have also applied in the man pages.
>
> Link: https://lore.kernel.org/all/agW4yMK6CinJGqXt@devuan/
> Suggested-by: Alejandro Colomar <alx@kernel.org>
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> ---
> include/uapi/linux/landlock.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
> index 10a346e55e95..48c12ddf1108 100644
> --- a/include/uapi/linux/landlock.h
> +++ b/include/uapi/linux/landlock.h
> @@ -255,16 +255,16 @@ struct landlock_net_port_attr {
> * :manpage:`connect(2)` as well as calls to :manpage:`sendmsg(2)` with an
> * explicit recipient address.
> *
> - * This access right only applies to connections to UNIX server sockets which
> + * This access right applies only to connections to UNIX server sockets which
> * were created outside of the newly created Landlock domain (e.g. from within
> * a parent domain or from an unrestricted process). Newly created UNIX
> * servers within the same Landlock domain continue to be accessible. In this
> * regard, %LANDLOCK_ACCESS_FS_RESOLVE_UNIX has the same semantics as the
> * ``LANDLOCK_SCOPE_*`` flags.
> *
> - * If a resolve attempt is denied, the operation returns an ``EACCES`` error,
> - * in line with other filesystem access rights (but different to denials for
> - * abstract UNIX domain sockets).
> + * If a resolution attempt is denied, the operation returns an ``EACCES``
> + * error, in line with other filesystem access rights (but different to
> + * denials for abstract UNIX domain sockets).
> *
> * This access right is available since the ninth version of the Landlock ABI.
> *
> --
> 2.54.0
>
>
^ permalink raw reply
* Re: [PATCH bpf-next v6 5/8] bpftool: Cover loader metadata with the program signature
From: Quentin Monnet @ 2026-07-08 8:55 UTC (permalink / raw)
To: Daniel Borkmann, ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-6-daniel@iogearbox.net>
On 08/07/2026 08:53, Daniel Borkmann wrote:
> bpftool_prog_sign() signed only the loader instructions. The metadata
> blob the loader installs was left to an in-loader hash check, which
> the kernel now performs at load time over insns || metadata.
>
> Sign that same concatenation: pass the metadata blob (gen_loader_opts
> data) through to bpftool_prog_sign() and feed insns || metadata to
> CMS_final(). The excl_prog_hash stays a digest of the instructions
> alone; it binds the metadata map to the loader and is matched against
> prog->digest by the verifier, independent of what the signature covers.
>
> The signed artifact is now plain data: both bytes the signature
> covers are embedded verbatim in the generated skeleton, so signing
> and verifying an lskel is an ordinary CMS operation that a signer or
> auditor can perform (or reproduce) offline, without analyzing loader
> bytecode to establish what the signature actually attests to.
>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Thanks!
^ permalink raw reply
* Re: [PATCH bpf-next v6 4/8] bpftool: Check EVP_Digest when computing excl_prog_hash
From: Quentin Monnet @ 2026-07-08 8:55 UTC (permalink / raw)
To: Daniel Borkmann, ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-5-daniel@iogearbox.net>
On 08/07/2026 08:53, Daniel Borkmann wrote:
> bpftool_prog_sign() ignores the return value of EVP_Digest(). If the
> digest computation fails (context allocation failure, or a digest
> fetch failure under OpenSSL), EVP_Digest() returns 0 and leaves the
> output buffer untouched, but the function still reports success.
>
> Fixes: 40863f4d6ef2 ("bpftool: Add support for signing BPF programs")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Bpftool changes look good to me, thanks for the fix.
Reviewed-by: Quentin Monnet <qmo@kernel.org>
^ permalink raw reply
* [PATCH bpf-next v6 8/8] Documentation/bpf: Add BPF signing and enforcement doc
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
Describe the BPF signing design end to end: why a trusted loader is
needed, the signature(insns || metadata) contract, load-time
verification via fd_array (exclusive + frozen maps), the binary
BPF_SIG_{UNSIGNED,VERIFIED} verdict, and how [BPF] LSMs can enforce
policy on it.
This writes down the contract on the discussion points with the LSM /
integrity folks [0][1]: by the time security_bpf_prog_load() is
called, signature verification has fully completed and covers the
instructions plus the frozen contents of every bound exclusive map;
there is no intermediate "loader verified, payload pending" state
to reason about; and what BPF_SIG_VERIFIED means at each hook is
spelled out explicitly.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/bc823ddbaf63e0e177eb46d1cc15076e4e2e689d.camel@HansenPartnership.com [0]
Link: https://lore.kernel.org/bpf/CAHC9VhSDkwGgPfrBUh7EgBKEJj_JjnY68c0YAmuuLT_i--GskQ@mail.gmail.com [1]
---
Documentation/bpf/index.rst | 1 +
Documentation/bpf/signing.rst | 497 ++++++++++++++++++++++++++++++++++
2 files changed, 498 insertions(+)
create mode 100644 Documentation/bpf/signing.rst
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 0d5c6f659266..638a00d42bc2 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -28,6 +28,7 @@ that goes into great technical depth about the BPF Architecture.
classic_vs_extended.rst
bpf_iterators
bpf_licensing
+ signing
test_debug
clang-notes
linux-notes
diff --git a/Documentation/bpf/signing.rst b/Documentation/bpf/signing.rst
new file mode 100644
index 000000000000..e73eaaebd8b1
--- /dev/null
+++ b/Documentation/bpf/signing.rst
@@ -0,0 +1,497 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+BPF signing
+============
+
+This document describes how BPF programs are cryptographically signed, how the
+kernel verifies them at load time, and how Linux Security Modules (LSMs) -
+including the BPF LSM - use the resulting verdict to enforce policy. It is
+written for developers who want to produce signed BPF objects, understand what
+the signature actually guarantees, or build a policy on top of it.
+
+Motivation
+==========
+
+A signed BPF program lets the kernel establish that the bytecode being loaded
+originates from a trusted producer and was not modified in transit. On its own
+the kernel does not *require* signatures - an unsigned program loads exactly as
+before - but it records a verdict (see `The verdict`_) that an LSM can gate on.
+This is the building block for policies such as "only run BPF that was signed by
+a key in the trusted keyring", as could in the future be enforced by an LSM
+such as IPE.
+
+Signing is orthogonal to the existing permission model: it does not replace the
+capability checks or the verifier. A signed load still requires the usual
+privileges (``CAP_BPF`` and any program-type-specific capability, subject to
+``kernel.unprivileged_bpf_disabled``), and the loader's instructions are still
+checked by the verifier like any other program. A valid signature establishes
+*origin and integrity*, not safety - it lets a policy trust where the bytecode
+came from, it does not let a load skip any check it would otherwise face.
+
+The hard part is *what* gets signed. A naive scheme would sign a program's
+instruction buffer at build time and verify that signature at
+``BPF_PROG_LOAD``. That does not survive contact with real BPF objects, because
+the bytes the kernel finally loads are not the bytes the developer built and
+signed. Between the two, libbpf and the kernel rewrite the program:
+
+- **map file descriptors** are patched into ``ld_imm64`` instructions
+ (``BPF_PSEUDO_MAP_FD``), and a map's fd is assigned at load time, so it
+ differs on every run;
+- **CO-RE relocations** rewrite field offsets, sizes and existence flags against
+ the *running* kernel's BTF, so the result differs from one kernel to the next;
+- **kfunc and ksym references** are resolved to ids/addresses in the running
+ kernel;
+- **global data** (``.rodata``/``.data``/``.bss``) is created and seeded as maps
+ at load.
+
+So a signature over the original instructions cannot match the relocated
+instructions the verifier ends up checking, and the relocated form cannot be
+produced ahead of time because it depends on the target kernel. There is no
+fixed byte string that is both signable at build time and what the kernel
+actually loads - which is why a program cannot simply be signed and loaded
+directly.
+
+The trusted loader
+==================
+
+The solution is to move that setup work *into* a small BPF program - the
+**loader** - and sign the loader instead of the individual programs. libbpf's
+``gen_loader`` machinery (``bpftool gen skeleton -L``, the "light skeleton")
+emits a ``BPF_PROG_TYPE_SYSCALL`` program whose body performs the bpf() syscalls
+that create maps, apply relocations, and load the real programs. The payload it
+installs - the serialized programs, map descriptions, relocation data and
+initial values - lives in a separate array map, the **metadata map**
+(``__loader.map``).
+
+So the unit of trust is the loader, and the signing contract is::
+
+ Sig(I_loader || D_meta)
+
+where ``I_loader`` is the loader's instruction stream and ``D_meta`` is the
+content of the metadata map. Verifying the loader's signature establishes that
+both the loader *and* the payload it is about to install are authentic. The
+loader is reproducible: ``gen_loader`` builds it from primitives so the same
+object yields the same bytes on any build host.
+
+Why the loader is signable when the program is not
+--------------------------------------------------
+
+The loader sidesteps every rewrite listed above, because the bytes that are
+signed are *relocation-invariant*:
+
+- The loader's own instructions are a fixed sequence of bpf() syscalls emitted
+ by ``gen_loader``; they carry no CO-RE relocations and resolve no ksyms, so
+ they are identical on every kernel. The metadata map is referenced by *index*
+ into ``fd_array`` (``BPF_PSEUDO_MAP_IDX_VALUE``), not by a baked-in file
+ descriptor, so even that reference does not change between build and load.
+ The loader instruction bytes the kernel verifies are exactly the bytes that
+ were signed.
+- The metadata map is opaque, frozen data - the serialized target programs,
+ their relocation records, map descriptions and initial values. Its bytes are
+ identical at build time and at load time, so they are simply appended to the
+ instructions and covered by the same signature (there is no separate metadata
+ hash to compute or compare).
+
+All the host-specific rewriting - creating maps, patching their fds into the
+target programs, applying CO-RE, resolving ksyms, seeding global data - still
+happens, but it happens *inside the loader at runtime*, on the verified
+metadata, **after** the kernel has verified the ``insns || metadata`` signature.
+The kernel never has to verify the relocated target programs: it verifies the
+loader and its inputs once, and trust transfers to whatever that now-trusted,
+deterministic loader installs. The relocation step is moved from "before the
+signature can be checked" to "after a trusted program runs" - which is exactly
+what makes it signable.
+
+Because the metadata map is the loader's only untrusted input, two existing map
+properties are reused to keep it trustworthy across the load:
+
+Exclusive maps
+ A map created with ``excl_prog_hash`` (see ``BPF_MAP_CREATE``) may only be
+ accessed by a program whose digest matches that hash. The verifier enforces
+ ``map->excl_prog_sha == prog->digest`` for every map a program uses, so the
+ metadata map is bound to exactly the signed loader and cannot be shared with
+ or mutated by another program.
+
+Frozen maps
+ The metadata map is frozen (``BPF_MAP_FREEZE``) before the loader is loaded.
+ Freezing blocks further userspace writes, so the bytes folded into the
+ signature cannot change before the loader runs. (Freezing does not make the
+ map read-only to the loader program itself, which still writes created file
+ descriptors back into the blob's scratch area.)
+
+Load-time verification
+=======================
+
+Rather than have the loader check its own metadata from within BPF, the kernel
+verifies it directly at ``BPF_PROG_LOAD``, with no new UAPI. The mechanism
+reuses the existing ``fd_array``:
+
+#. Userspace creates the metadata map with ``excl_prog_hash`` set to the
+ loader's digest, populates it, and freezes it.
+#. The loader is loaded with ``signature``/``signature_size``/``keyring_id``
+ set, the metadata map referenced through ``fd_array``, and ``fd_array_cnt``
+ set so the kernel knows the array's length.
+#. Signature verification runs inside the verifier (``bpf_check()``), once it
+ has resolved the ``fd_array`` entries into the program's ``used_maps``. The
+ maps folded into the signature are therefore the very objects the program
+ binds - a single resolution of ``fd_array``, not a separate read, so the
+ verified bytes cannot be swapped for a different map after the check (no
+ time-of-check/time-of-use window). Each folded map must be exclusive (carry
+ ``excl_prog_sha``) and a plain array map (``BPF_MAP_TYPE_ARRAY``); only an
+ array map exposes its value buffer through ``map_direct_value_addr()`` as a
+ kernel address spanning ``value_size`` bytes. A map that is not exclusive, not
+ frozen, or not a plain array is rejected, with a verifier log message naming
+ the offending map. The kernel appends each map's frozen
+ contents to the instruction buffer and verifies the PKCS#7 signature over the
+ concatenation ``insns || metadata_0 || metadata_1 || ...`` in ``used_maps``
+ order, before it rewrites the (signed) instructions.
+
+A signed program therefore takes one of exactly two shapes, both fully
+supported:
+
+- **No bound maps** (``fd_array_cnt == 0``): there is nothing to append, so the
+ kernel verifies the signature over the instructions alone. A valid signature
+ yields ``BPF_SIG_VERIFIED`` and the program loads. This is the ordinary case
+ for a directly-loaded signed program with no separate payload; it is *not*
+ rejected for "missing" metadata, because it has none to cover.
+- **Exclusive bound maps** (``fd_array_cnt > 0``): every entry is exclusive and
+ folded, so the signature covers ``insns || metadata``.
+
+There is no third shape: a non-exclusive map in a signed program's ``fd_array``
+is rejected rather than silently left out of the signature, so a signed loader
+never binds a map its signature does not cover.
+
+The digest binding (``excl_prog_sha == prog->digest``) is enforced by the
+verifier as usual; because that check runs while ``fd_array`` is resolved -
+before the verifier would otherwise compute the tag - ``prog->digest`` is
+computed up front in the verifier, over the unmodified (signature-covered)
+instructions, for any signed load.
+
+Coverage is then enforced as the verifier resolves instructions, at the point
+each object is bound rather than by a count taken afterwards. Once the signature
+has been verified, binding any further map is refused: a map reached by a
+directly-referenced fd, or a map swapped into an ``fd_array`` slot the loader
+reads, is not among those already folded, so it is rejected the moment the
+verifier tries to bind it. A BTF is refused outright for a signed program - a
+ksym or a BTF fd in ``fd_array``, whether resolved up front or lazily for a
+module kfunc, is rejected when it would be bound. Together with the fold rule
+above this keeps the verdict binary: a signed program cannot use a map its
+signature does not cover, and a different but equally digest-bound map cannot be
+substituted at an ``fd_array`` slot. Non-exclusive maps are never folded, so a
+signed program cannot use one at all.
+
+The verdict
+===========
+
+A program is either unsigned or fully verified - there is no intermediate
+state. The outcome is recorded in ``prog->aux->sig.verdict``:
+
+.. code-block:: c
+
+ enum bpf_sig_verdict {
+ BPF_SIG_UNSIGNED = 0,
+ BPF_SIG_VERIFIED,
+ };
+
+``BPF_SIG_VERIFIED`` means the signature is valid and covers the instructions
+*and* the frozen contents of every exclusive map the program uses:
+
+- For an ordinary, directly-loaded signed program the instructions are the whole
+ artifact and it uses no exclusive maps, so a valid instruction signature is
+ the complete verification.
+- For a signed loader the metadata map is exclusive, so its contents are folded
+ in and the signature covers ``insns || metadata``.
+
+There is deliberately no "instructions verified but metadata not" verdict: a
+signed loader that fails to cover its metadata is *rejected* (see above), not
+recorded with a weaker verdict. ``BPF_SIG_VERIFIED`` therefore always means the
+program and everything the signature is responsible for are authentic, which is
+what a policy can rely on.
+
+Alongside the verdict the kernel records which keyring validated the signature;
+see `Keyrings`_.
+
+Enforcement via LSMs
+====================
+
+Signing only *records* a verdict; an LSM turns it into policy. The verdict and
+keyring fields live in ``struct bpf_prog_aux``, so a BPF LSM program can read
+them directly (see Documentation/bpf/prog_lsm.rst for writing and attaching BPF
+LSM programs); the same fields are equally available to in-tree LSMs. Two hooks
+are useful at different points of the load: the dedicated
+``security_bpf_prog_load()`` gates admission before the main verification work,
+and the existing ``security_bpf_prog()`` observes a program that has fully
+loaded.
+
+Admission: ``security_bpf_prog_load()``
+---------------------------------------
+
+This hook gates admission **for every load**, from a single call site inside the
+verifier (``bpf_check()``), before the main verification work. It runs after the
+optional signature verification, so the verdict and keyring fields are final - the
+hook can see whether, and how strongly, the program was signed, which keyring
+validated it, the load ``attr``, the BPF token and whether the load came from the
+kernel. For a signed load the verdict is ``BPF_SIG_VERIFIED`` here (the signature
+has just been checked); for an unsigned load it is ``BPF_SIG_UNSIGNED``.
+
+This is the place for *coarse admission* that must also see unsigned and
+not-yet-verified loads: require a signature at all, restrict the acceptable
+keyring, restrict which token/credentials may load BPF, apply per-program-type
+rules, or audit every load attempt that makes it past signature verification -
+attempts failing the signature or the metadata binding abort before this hook
+fires. It is the primary deny point.
+
+One subtlety: this hook runs *before* the verifier finishes its work, so
+``BPF_SIG_VERIFIED`` *here* means only "validly signed" - not "loaded". Allowing
+a load at this point lets it *proceed*; it does not guarantee the program will
+load. A validly signed program can still be rejected afterwards on two
+independent grounds: the verifier may reject it like any other program (unsafe
+memory access, bad control flow, resource limits, ...), and the kernel separately
+refuses - as the verifier resolves instructions and binds each object - any map
+the signature does not cover or any BTF at all, regardless of what this hook
+returned. Only after the program has fully loaded, at the next hook
+(``security_bpf_prog()``), does ``BPF_SIG_VERIFIED`` carry its full meaning:
+validly signed *and* fully verified.
+
+A more realistic admission policy than "is it signed at all": accept programs
+signed by a system keyring, accept a user-keyring signature only if the
+key/keyring it was verified against is on an explicit allowlist, and emit a
+tamper-evident record of every decision so that even denied attempts are
+auditable. (Illustrative - error checking elided.)
+
+.. code-block:: c
+
+ /* Serials of user keys/keyrings we additionally trust. */
+ struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __type(key, __s32); /* keyring_serial */
+ __type(value, __u8);
+ __uint(max_entries, 64);
+ } trusted_user_keys SEC(".maps");
+
+ /* Audit stream consumed by a userspace logger. */
+ struct {
+ __uint(type, BPF_MAP_TYPE_RINGBUF);
+ __uint(max_entries, 1 << 16);
+ } audit SEC(".maps");
+
+ struct decision { __u32 prog_type, verdict, ktype; __s32 serial, ret; };
+
+ SEC("lsm/bpf_prog_load")
+ int BPF_PROG(admit, struct bpf_prog *prog, union bpf_attr *attr,
+ struct bpf_token *token, bool kernel)
+ {
+ __u32 verdict = prog->aux->sig.verdict;
+ __u32 ktype = prog->aux->sig.keyring_type;
+ __s32 serial = prog->aux->sig.keyring_serial;
+ struct decision *d;
+ int ret = 0;
+
+ if (kernel)
+ return 0; /* trust in-kernel loads */
+
+ if (verdict != BPF_SIG_VERIFIED)
+ ret = -EPERM; /* must be validly signed */
+ else if (ktype == BPF_SIG_KEYRING_USER &&
+ !bpf_map_lookup_elem(&trusted_user_keys, &serial))
+ ret = -EPERM; /* key/keyring not allowlisted */
+
+ d = bpf_ringbuf_reserve(&audit, sizeof(*d), 0);
+ if (d) {
+ d->prog_type = attr->prog_type;
+ d->verdict = verdict;
+ d->ktype = ktype;
+ d->serial = serial;
+ d->ret = ret;
+ bpf_ringbuf_submit(d, 0); /* record allow *and* deny */
+ }
+ return ret;
+ }
+
+Observing a verified load: ``security_bpf_prog()``
+--------------------------------------------------
+
+There is deliberately no separate "metadata attested" hook. The coverage check
+above is enforced by the kernel unconditionally, so a signed loader that fails
+to cover its metadata never loads and an LSM never has to re-establish that
+fact. To *act on* a program that has successfully and fully loaded, use the
+existing ``security_bpf_prog()`` hook (``lsm/bpf_prog``), which fires from
+``bpf_prog_new_fd()`` - after the verifier, after the coverage check, and after
+``bpf_prog_alloc_id()``. Relative to the admission hook this point is strictly
+later and stronger:
+
+- the program has an id (``prog->aux->id``), so it can be recorded or correlated
+ with later events;
+- ``verdict == BPF_SIG_VERIFIED`` *here* means **fully** verified - a program
+ that used a map the signature does not cover was already rejected, so it cannot
+ reach this point;
+- it observes only programs that actually loaded; a failed load never mints an
+ fd, so it never reaches this hook.
+
+It takes only the ``prog`` and a non-zero return still aborts (the fd is not
+handed out), so it can veto as well as observe. One wrinkle: it also fires on
+other paths that mint a new program fd - notably ``bpf_prog_get_fd_by_id()`` -
+not just on a fresh load. Because the program already has its id here, an LSM
+can tell the two apart with a small hash map: the *first* time an id is seen is
+the load; a later sighting of the same id is just another fd to a program that
+already exists.
+
+To bound the map and let a reused id read as a fresh load, this can be paired
+with ``security_bpf_prog_free()`` (``lsm/bpf_prog_free``), which deletes the
+entry on teardown - keyed by the same ``prog`` pointer, since
+``bpf_prog_free_id()`` has already cleared ``prog->aux->id`` to ``0`` by the time
+that hook runs. (Illustrative - privileged LSM, error checking elided.)
+
+.. code-block:: c
+
+ struct rec { __u32 id, ktype; __s32 serial; };
+
+ struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __type(key, __u64); /* struct bpf_prog * -- stable id */
+ __type(value, struct rec);
+ __uint(max_entries, 4096);
+ } live SEC(".maps");
+
+ SEC("lsm/bpf_prog") /* fires after load and on every later fd */
+ int BPF_PROG(observe, struct bpf_prog *prog)
+ {
+ __u64 key = (__u64)(unsigned long)prog;
+ struct rec r;
+
+ if (prog->aux->sig.verdict != BPF_SIG_VERIFIED)
+ return 0;
+ if (bpf_map_lookup_elem(&live, &key))
+ return 0; /* seen before: a later fd, not a load */
+
+ /* First sighting == this program just loaded; id is valid here. */
+ r.id = prog->aux->id;
+ r.ktype = prog->aux->sig.keyring_type;
+ r.serial = prog->aux->sig.keyring_serial;
+ bpf_map_update_elem(&live, &key, &r, BPF_NOEXIST);
+ /* ... newly-loaded verified-program action, e.g. record r.id ... */
+ return 0;
+ }
+
+Putting them together: to *require* verified BPF, deny at the admission hook
+unless the verdict is ``BPF_SIG_VERIFIED`` (and, if desired, restrict the
+keyring). The kernel then guarantees that any program which actually loads with
+that verdict covered all of its exclusive maps, rejecting any that did not - so
+a deny-by-default admission policy needs no second enforcement point. Use
+``security_bpf_prog()`` to record or finally gate the verified programs once
+they carry an id. The ``verdict``, ``keyring_type`` and ``keyring_serial`` fields
+let a policy distinguish, for example, "verified and signed by a builtin key"
+from "verified by a user key". A policy LSM such as IPE could consume the same
+hooks to enforce system policy without writing any BPF, though none implements
+this today.
+
+Keyrings
+========
+
+``keyring_id`` selects the trusted keyring the PKCS#7 signature is verified
+against. The well-known ids ``0`` (builtin), ``VERIFY_USE_SECONDARY_KEYRING``
+and ``VERIFY_USE_PLATFORM_KEYRING`` select the corresponding system keyrings;
+any other value is treated as the serial of a user/session key or keyring.
+The keyring is looked up first, before the signature bytes are examined, so a
+signature naming a non-existent keyring is rejected up front, and a failed
+verification aborts the load - so a program that loads successfully with a
+signature always has consistent keyring fields recorded.
+
+Two fields are recorded in ``prog->aux->sig`` for an LSM to inspect:
+
+``keyring_type`` (``enum bpf_sig_keyring``)
+ Classified purely from ``keyring_id`` whenever the program is signed:
+ ``BPF_SIG_KEYRING_BUILTIN``, ``_SECONDARY``, ``_PLATFORM`` for the system
+ keyrings, or ``_USER`` for a user/session keyring. It is
+ ``BPF_SIG_KEYRING_NONE`` for an unsigned program.
+
+``keyring_serial`` (``s32``)
+ Set **only** on a successful verification, to the serial of the
+ **user/session key or keyring** that ``keyring_id`` resolved to - the
+ object the signature was verified against, not the individual asymmetric
+ key inside it that matched the signer. Passing
+ ``KEY_SPEC_SESSION_KEYRING``, for example, records the session keyring's
+ serial. The system keyrings are trusted as a whole and expose no serial
+ here, so the serial is ``0`` for builtin, secondary and platform
+ signatures, and ``0`` for unsigned programs. In other words, a non-zero
+ ``keyring_serial`` is exactly "verified against the user key/keyring with
+ this serial".
+
+.. list-table::
+ :header-rows: 1
+
+ * - ``keyring_id``
+ - ``keyring_type``
+ - ``keyring_serial``
+ * - (no signature)
+ - ``BPF_SIG_KEYRING_NONE``
+ - ``0``
+ * - ``0``
+ - ``BPF_SIG_KEYRING_BUILTIN``
+ - ``0``
+ * - ``VERIFY_USE_SECONDARY_KEYRING``
+ - ``BPF_SIG_KEYRING_SECONDARY``
+ - ``0``
+ * - ``VERIFY_USE_PLATFORM_KEYRING``
+ - ``BPF_SIG_KEYRING_PLATFORM``
+ - ``0``
+ * - other (a user/session key serial)
+ - ``BPF_SIG_KEYRING_USER``
+ - serial of the resolved key/keyring
+
+Producing a signed object
+==========================
+
+``bpftool`` generates and signs a light skeleton in one step::
+
+ bpftool gen skeleton -L -S -k <private_key.pem> -i <certificate.x509> \
+ obj.bpf.o > obj.lskel.h
+
+``-L`` selects the light-skeleton (``gen_loader``) backend and ``-S`` enables
+signing; ``-k`` and ``-i`` supply the signing key and its X.509 certificate.
+``bpftool`` signs ``insns || metadata`` - the exact bytes the kernel
+reconstructs - and also computes ``excl_prog_hash`` as the digest of the loader
+instructions so the metadata map can be bound to the loader. The signature and
+hash are embedded in the generated header; the certificate is used only for
+signing and is not included. Loading the skeleton performs the
+create/populate/freeze/load sequence described above.
+
+At runtime the trusted public key must be present in the chosen keyring (for
+example added to the session keyring, or built into the kernel's builtin trusted
+keyring) for verification to succeed.
+
+UAPI reference
+==============
+
+``BPF_PROG_LOAD`` (``union bpf_attr``):
+
+``signature``, ``signature_size``
+ Pointer to and length of the PKCS#7 signature blob.
+
+``keyring_id``
+ Trusted keyring selector (see `Keyrings`_).
+
+``fd_array``, ``fd_array_cnt``
+ Array of map (and module BTF) file descriptors bound to the program.
+ ``fd_array_cnt`` must be set for the kernel to scan the array. When a
+ signature is present, a BTF entry is rejected outright, and every map must
+ be exclusive; its frozen contents are folded into the verified buffer, and
+ a non-exclusive entry is rejected.
+
+``BPF_MAP_CREATE`` (``union bpf_attr``):
+
+``excl_prog_hash``, ``excl_prog_hash_size``
+ SHA-256 digest of the program permitted to access this (exclusive) map. This
+ binds the metadata map to the loader; it is not a hash of the map *content*.
+ The map content is not hashed separately at all - it is covered, as bytes,
+ by the program signature.
+
+Notes and limitations
+======================
+
+- The instructions plus folded metadata are verified as one ``bpf_dynptr``,
+ which bounds the combined size (currently ~16 MiB); very large objects can
+ exceed it.
+- The metadata container is a single-element array map, accessed through
+ ``map_direct_value_addr``.
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 7/8] selftests/bpf: Verify load-time signed loader metadata
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
The signed gen_loader no longer checks its metadata map from within
BPF; the kernel does it at BPF_PROG_LOAD by folding the loader's frozen
exclusive fd_array maps into the signature. Exercise that path end to
end. Extend with more test cases (e.g. map-less program, asserting the
LSM admission hook observes BPF_SIG_UNSIGNED and BPF_SIG_VERIFIED), and
retire the subtests that asserted the old in-loader check, which no
longer exists.
# LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t signed_loader
[...]
#412/1 signed_loader/loadtime_no_map:OK
#412/2 signed_loader/loadtime_with_map:OK
#412/3 signed_loader/metadata_match:OK
#412/4 signed_loader/signature_enforced:OK
#412/5 signed_loader/signed_nonexcl_fd_array_rejected:OK
#412/6 signed_loader/signed_unfrozen_fd_array_rejected:OK
#412/7 signed_loader/signed_nonarray_fd_array_rejected:OK
#412/8 signed_loader/signed_btf_fd_array_rejected:OK
#412/9 signed_loader/signed_module_kfunc_rejected:OK
#412/10 signed_loader/signature_failure_logs:OK
#412/11 signed_loader/signature_too_large:OK
#412/12 signed_loader/signature_zero_size:OK
#412/13 signed_loader/signature_bad_keyring:OK
#412/14 signed_loader/metadata_ctx_max_entries_ignored:OK
#412/15 signed_loader/metadata_ctx_initial_value_ignored:OK
#412/16 signed_loader/signature_authenticates_insns:OK
#412/17 signed_loader/signature_authenticates_metadata:OK
#412/18 signed_loader/hash_requires_frozen:OK
#412/19 signed_loader/no_update_after_freeze:OK
#412/20 signed_loader/freeze_writable_mmap:OK
#412/21 signed_loader/no_writable_mmap_frozen:OK
#412/22 signed_loader/map_hash_matches_libbpf:OK
#412/23 signed_loader/map_hash_multi_element:OK
#412/24 signed_loader/map_hash_bad_size:OK
#412/25 signed_loader/map_hash_unsupported_type:OK
#412/26 signed_loader/lsm_signature_verdict:OK
#412/27 signed_loader/signed_no_fd_array:OK
#412/28 signed_loader/signed_map_by_fd_rejected:OK
#412/29 signed_loader/signed_sparse_fd_array_rejected:OK
#412 signed_loader:OK
Summary: 1/29 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
.../selftests/bpf/prog_tests/signed_loader.c | 1025 ++++++++++++++---
.../selftests/bpf/progs/test_signed_loader.c | 9 +-
2 files changed, 866 insertions(+), 168 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/signed_loader.c b/tools/testing/selftests/bpf/prog_tests/signed_loader.c
index 5fc417e31fc6..0019492cf07a 100644
--- a/tools/testing/selftests/bpf/prog_tests/signed_loader.c
+++ b/tools/testing/selftests/bpf/prog_tests/signed_loader.c
@@ -11,6 +11,8 @@
#include <linux/keyctl.h>
#include <linux/bpf.h>
+#include <bpf/btf.h>
+
#include "bpf/libbpf_internal.h" /* for libbpf_sha256() */
#include "bpf/skel_internal.h" /* for loader ctx layout (bpf_loader_ctx etc) */
@@ -19,8 +21,6 @@
#include "test_signed_loader_data.skel.h"
#include "test_signed_loader_lsm.skel.h"
-#define SIG_MATCH_INSNS 33 /* excl (5) + 4 * sha-dword (7) */
-
enum {
BPF_SIG_UNSIGNED = 0,
BPF_SIG_VERIFIED,
@@ -35,7 +35,8 @@ enum {
};
static int load_loader(const void *insns, __u32 insns_sz, int map_fd,
- const void *sig, __u32 sig_sz, __s32 keyring_id)
+ const void *sig, __u32 sig_sz, __s32 keyring_id,
+ __u32 fd_array_cnt)
{
union bpf_attr attr;
int fd;
@@ -52,6 +53,7 @@ static int load_loader(const void *insns, __u32 insns_sz, int map_fd,
attr.signature_size = sig_sz;
attr.keyring_id = keyring_id;
}
+ attr.fd_array_cnt = fd_array_cnt;
memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
offsetofend(union bpf_attr, keyring_id));
@@ -62,14 +64,12 @@ static int run_gen_loader(const void *insns, __u32 insns_sz,
const void *data, __u32 data_sz,
const void *excl, __u32 excl_sz,
const void *sig, __u32 sig_sz,
- bool get_hash, void *ctx, __u32 ctx_sz, bool *loader_ran)
+ void *ctx, __u32 ctx_sz, bool *loader_ran)
{
LIBBPF_OPTS(bpf_map_create_opts, mopts,
.excl_prog_hash = excl,
.excl_prog_hash_size = excl_sz);
- __u8 hbuf[SHA256_DIGEST_LENGTH];
- struct bpf_map_info info;
- __u32 ilen = sizeof(info), key = 0;
+ __u32 key = 0;
union bpf_attr attr;
int map_fd, prog_fd, ret;
@@ -87,15 +87,6 @@ static int run_gen_loader(const void *insns, __u32 insns_sz,
ret = -errno;
goto out_map;
}
- if (get_hash) {
- memset(&info, 0, sizeof(info));
- info.hash = ptr_to_u64(hbuf);
- info.hash_size = sizeof(hbuf);
- if (bpf_map_get_info_by_fd(map_fd, &info, &ilen)) {
- ret = -errno;
- goto out_map;
- }
- }
memset(&attr, 0, sizeof(attr));
attr.prog_type = BPF_PROG_TYPE_SYSCALL;
@@ -108,6 +99,7 @@ static int run_gen_loader(const void *insns, __u32 insns_sz,
attr.signature = ptr_to_u64(sig);
attr.signature_size = sig_sz;
attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ attr.fd_array_cnt = 1;
}
memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
@@ -236,79 +228,6 @@ static int sign_buf(const char *dir, const void *buf, __u32 len,
return ret;
}
-static void check_sig_match_shape(const struct bpf_insn *in, int n)
-{
- int a = -1, cleanup = -1, i, base, t, br[5], nb = 0;
-
- /* BPF_PSEUDO_MAP_IDX (the struct bpf_map * form) is used only here. */
- for (i = 0; i + 1 < n; i++) {
- if (in[i].code == (BPF_LD | BPF_IMM | BPF_DW) &&
- in[i].src_reg == BPF_PSEUDO_MAP_IDX) {
- a = i;
- break;
- }
- }
- if (!ASSERT_GE(a, 0, "emit_signature_match present"))
- return;
- if (!ASSERT_LE(a + SIG_MATCH_INSNS, n, "block fits in program"))
- return;
-
- /* excl check: r2 = *(u32 *)(map + 32); if r2 != 1 goto cleanup */
- ASSERT_EQ(in[a + 2].code, (BPF_LDX | BPF_MEM | BPF_W), "excl load width");
- ASSERT_EQ(in[a + 2].off, SHA256_DIGEST_LENGTH, "excl field offset");
- ASSERT_EQ(in[a + 4].code, (BPF_JMP | BPF_JNE | BPF_K), "excl branch op");
- ASSERT_EQ(in[a + 4].imm, 1, "excl compared to 1");
- br[nb++] = a + 4;
-
- /* 4 sha-dword checks: r2 = *(u64 *)(map + i*8); if r2 != r3 goto cleanup */
- for (i = 0; i < 4; i++) {
- base = a + 5 + i * 7;
- ASSERT_EQ(in[base + 2].code, (BPF_LDX | BPF_MEM | BPF_DW), "sha load width");
- ASSERT_EQ(in[base + 2].off, i * 8, "sha dword offset");
- ASSERT_EQ(in[base + 3].code, (BPF_LD | BPF_IMM | BPF_DW), "sha imm64 (H_meta)");
- ASSERT_EQ(in[base + 6].code, (BPF_JMP | BPF_JNE | BPF_X), "sha branch op");
- br[nb++] = base + 6;
- }
-
- /*
- * Locate the real cleanup label so we can pin the exact jump target,
- * not just "some backward label". bpf_gen__init() emits the cleanup
- * block as a prog-fd close loop whose first instruction is the label
- * every error branch jumps to.
- */
- for (i = 0; i + 2 < a; i++) {
- if (in[i].code == (BPF_LDX | BPF_MEM | BPF_W) &&
- in[i].dst_reg == BPF_REG_1 && in[i].src_reg == BPF_REG_10 &&
- in[i + 1].code == (BPF_JMP | BPF_JSLE | BPF_K) &&
- in[i + 1].dst_reg == BPF_REG_1 && in[i + 1].imm == 0 &&
- in[i + 1].off == 1 &&
- in[i + 2].code == (BPF_JMP | BPF_CALL) &&
- in[i + 2].imm == BPF_FUNC_sys_close) {
- cleanup = i;
- break;
- }
- }
- if (!ASSERT_GE(cleanup, 0, "cleanup label located"))
- return;
- for (i = 0; i < nb; i++) {
- t = br[i] + 1 + in[br[i]].off;
- ASSERT_EQ(t, cleanup, "sig-match lands on cleanup");
- }
- /*
- * Same invariant for every other cleanup-bound jump in the program:
- * emit_check_err() is the only source of "if (r7 < 0) goto cleanup",
- * so each of those must also resolve exactly to cleanup.
- */
- for (i = 0, t = 0; i < n; i++) {
- if (in[i].code != (BPF_JMP | BPF_JSLT | BPF_K) ||
- in[i].dst_reg != BPF_REG_7 || in[i].imm != 0 || in[i].off >= 0)
- continue;
- ASSERT_EQ(i + 1 + in[i].off, cleanup, "err-check lands on cleanup");
- t++;
- }
- ASSERT_GT(t, 0, "found emit_check_err jumps");
-}
-
struct gen_loader_fixture {
struct test_signed_loader *skel;
struct gen_loader_opts gopts;
@@ -372,16 +291,6 @@ static void gen_loader_fixture_fini(struct gen_loader_fixture *f)
test_signed_loader__destroy(f->skel);
}
-static void metadata_check_shape(void)
-{
- struct gen_loader_fixture f;
-
- if (gen_loader_fixture_init(&f) == 0)
- check_sig_match_shape((const struct bpf_insn *)f.gopts.insns,
- f.gopts.insns_sz / sizeof(struct bpf_insn));
- gen_loader_fixture_fini(&f);
-}
-
static void metadata_match(void)
{
struct gen_loader_fixture f;
@@ -391,94 +300,263 @@ static void metadata_match(void)
if (gen_loader_fixture_init(&f) == 0) {
r = run_gen_loader(f.gopts.insns, f.gopts.insns_sz, f.blob,
f.data_sz, f.excl, sizeof(f.excl), NULL, 0,
- true, f.ctx, f.ctx_sz, &ran);
+ f.ctx, f.ctx_sz, &ran);
ASSERT_TRUE(ran, "loader ran");
ASSERT_EQ(r, 0, "honest loader retval");
}
gen_loader_fixture_fini(&f);
}
-static void metadata_sha_mismatch(void)
+static void signature_enforced(void)
{
+ static const __u8 junk[64] = { 0x30, 0x42, 0x13, 0x37, };
struct gen_loader_fixture f;
- bool ran;
- int r;
+ int fd;
if (gen_loader_fixture_init(&f) == 0) {
/*
- * blob[0] lives in the loader's fd_array scratch (first add_data in
- * bpf_gen__init); a 0-map program never reads it, so flipping it
- * changes only map->sha. The metadata check is the only thing that
- * can notice -> isolates emit_signature_match.
+ * A present-but-invalid signature (the cert bytes are not a
+ * PKCS#7 signature) must be rejected at load: the signature
+ * path is honored, not ignored. (The valid path is covered by
+ * the signed lskels.) Pin -EBADMSG, the PKCS#7 parse failure:
+ * a looser fd < 0 check could also be satisfied by the sparse
+ * fd_array rejection (-EACCES) that the loader's map reference
+ * would trip even if the signature were silently ignored.
*/
- f.blob[0] ^= 0xff;
- r = run_gen_loader(f.gopts.insns, f.gopts.insns_sz, f.blob,
- f.data_sz, f.excl, sizeof(f.excl), NULL, 0,
- true, f.ctx, f.ctx_sz, &ran);
- ASSERT_TRUE(ran, "loader ran");
- ASSERT_EQ(r, -EINVAL, "tampered blob rejected by emit_signature_match");
+ fd = load_loader(f.gopts.insns, f.gopts.insns_sz, -1, junk,
+ sizeof(junk), KEY_SPEC_SESSION_KEYRING, 0);
+ ASSERT_EQ(fd, -EBADMSG, "invalid signature rejected at load");
}
gen_loader_fixture_fini(&f);
}
-static void metadata_not_exclusive(void)
+static void signed_nonexcl_fd_array_rejected(void)
{
+ static const __u8 junk[64] = { 0x30, 0x42, 0x13, 0x37, };
struct gen_loader_fixture f;
- bool ran;
- int r;
+ int map_fd, fd;
if (gen_loader_fixture_init(&f) == 0) {
/*
- * Correct blob but a non-exclusive metadata map: the verifier does
- * not reject (excl_prog_sha unset), so the runtime map->excl == 1
- * check in the loader must.
+ * A signed program may only bind exclusive maps through fd_array
+ * (their contents are folded into the signature). Binding a
+ * non-exclusive map is rejected, before the signature is even
+ * examined.
*/
- r = run_gen_loader(f.gopts.insns, f.gopts.insns_sz, f.blob,
- f.data_sz, NULL, 0, NULL, 0, true, f.ctx,
- f.ctx_sz, &ran);
- ASSERT_TRUE(ran, "loader ran");
- ASSERT_EQ(r, -EINVAL, "non-exclusive metadata map rejected");
+ map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "nonexcl", 4,
+ f.data_sz, 1, NULL);
+ if (ASSERT_OK_FD(map_fd, "nonexcl_map")) {
+ if (ASSERT_OK(bpf_map_freeze(map_fd), "freeze")) {
+ fd = load_loader(f.gopts.insns, f.gopts.insns_sz,
+ map_fd, junk, sizeof(junk),
+ KEY_SPEC_SESSION_KEYRING, 1);
+ ASSERT_EQ(fd, -EPERM,
+ "non-exclusive map in signed fd_array rejected");
+ if (fd >= 0)
+ close(fd);
+ }
+ close(map_fd);
+ }
}
gen_loader_fixture_fini(&f);
}
-static void metadata_hash_not_computed(void)
+static void signed_unfrozen_fd_array_rejected(void)
{
+ static const __u8 junk[64] = { 0x30, 0x42, 0x13, 0x37, };
+ LIBBPF_OPTS(bpf_map_create_opts, mopts);
struct gen_loader_fixture f;
- bool ran;
- int r;
+ __u32 key = 0;
+ int map_fd, fd;
if (gen_loader_fixture_init(&f) == 0) {
/*
- * Correct, exclusive, frozen map, but its hash was never computed
- * (no OBJ_GET_INFO_BY_FD), so map->sha stays zero. The loader must
- * fail closed rather than treat an unset hash as a match.
+ * The metadata map must be frozen before a signed load so the
+ * folded bytes cannot change afterwards. Bind an exclusive map
+ * with matching contents but skip the freeze: the load must be
+ * rejected by the frozen check with -EPERM. The exclusivity
+ * check right after it would pass, so the errno uniquely pins
+ * the freeze requirement.
*/
- r = run_gen_loader(f.gopts.insns, f.gopts.insns_sz, f.blob,
- f.data_sz, f.excl, sizeof(f.excl), NULL, 0,
- false, f.ctx, f.ctx_sz, &ran);
- ASSERT_TRUE(ran, "loader ran");
- ASSERT_EQ(r, -EINVAL, "uncomputed metadata hash rejected");
+ mopts.excl_prog_hash = f.excl;
+ mopts.excl_prog_hash_size = sizeof(f.excl);
+ map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "unfrozen", 4,
+ f.data_sz, 1, &mopts);
+ if (ASSERT_OK_FD(map_fd, "unfrozen_map")) {
+ if (ASSERT_OK(bpf_map_update_elem(map_fd, &key, f.blob, 0),
+ "update")) {
+ fd = load_loader(f.gopts.insns, f.gopts.insns_sz,
+ map_fd, junk, sizeof(junk),
+ KEY_SPEC_SESSION_KEYRING, 1);
+ ASSERT_EQ(fd, -EPERM,
+ "unfrozen map in signed fd_array rejected");
+ if (fd >= 0)
+ close(fd);
+ }
+ close(map_fd);
+ }
}
gen_loader_fixture_fini(&f);
}
-static void signature_enforced(void)
+static void signed_nonarray_fd_array_rejected(void)
+{
+ static const __u8 junk[64] = { 0x30, 0x42, 0x13, 0x37, };
+ LIBBPF_OPTS(bpf_map_create_opts, mopts);
+ struct gen_loader_fixture f;
+ int map_fd, fd;
+
+ if (gen_loader_fixture_init(&f) == 0) {
+ /*
+ * Only a plain BPF_MAP_TYPE_ARRAY may be folded into the
+ * signature. An exclusive map of any other type is rejected
+ * (-EINVAL) rather than folded - this is the type gate that
+ * keeps arena maps (map_direct_value_addr() returns a user
+ * address) and insn-array maps (buffer smaller than value_size)
+ * out of the hashed region, where the old code would have
+ * memcpy()'d from them. A hash map stands in here: it is
+ * exclusive (bound to the loader digest) but not an array.
+ */
+ mopts.excl_prog_hash = f.excl;
+ mopts.excl_prog_hash_size = sizeof(f.excl);
+ map_fd = bpf_map_create(BPF_MAP_TYPE_HASH, "excl_hash", 4, 4, 1,
+ &mopts);
+ if (ASSERT_OK_FD(map_fd, "excl_hash_map")) {
+ fd = load_loader(f.gopts.insns, f.gopts.insns_sz, map_fd,
+ junk, sizeof(junk),
+ KEY_SPEC_SESSION_KEYRING, 1);
+ ASSERT_EQ(fd, -EINVAL,
+ "non-array map in signed fd_array rejected");
+ if (fd >= 0)
+ close(fd);
+ close(map_fd);
+ }
+ }
+ gen_loader_fixture_fini(&f);
+}
+
+static int setup_meta_map(const struct gen_loader_fixture *f);
+
+static void signed_btf_fd_array_rejected(void)
+{
+ char dir_tmpl[] = "/tmp/signed_loader_btfXXXXXX", *dir = NULL;
+ __u32 sig_sz = 8192;
+ int map_fd = -1, prog_fd = -1;
+ unsigned char *buf = NULL;
+ struct gen_loader_fixture f;
+ bool have_fixture = false;
+ struct btf *btf = NULL;
+ union bpf_attr attr;
+ int fds[2];
+ __u8 sig[8192];
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ return;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ return;
+ }
+ have_fixture = true;
+ if (gen_loader_fixture_init(&f) != 0)
+ goto out;
+
+ /*
+ * fd_array binds maps and BTFs alike, but only exclusive array maps are
+ * folded into the signature. Build an otherwise genuinely signed load -
+ * insns || metadata, exclusive frozen map at fd_array[0] - then smuggle
+ * an extra BTF into fd_array[1]. A signed program may not bind any BTF,
+ * so resolving the fd_array entries rejects the BTF with -EACCES (in
+ * __add_used_btf(), before the signature is even verified).
+ */
+ buf = malloc((size_t)f.gopts.insns_sz + f.data_sz);
+ if (!ASSERT_OK_PTR(buf, "signbuf"))
+ goto out;
+ memcpy(buf, f.gopts.insns, f.gopts.insns_sz);
+ memcpy(buf + f.gopts.insns_sz, f.blob, f.data_sz);
+ if (!ASSERT_OK(sign_buf(dir, buf, f.gopts.insns_sz + f.data_sz, sig,
+ &sig_sz), "sign insns||metadata"))
+ goto out;
+
+ map_fd = setup_meta_map(&f);
+ if (!ASSERT_OK_FD(map_fd, "meta_map"))
+ goto out;
+ btf = btf__new_empty();
+ if (!ASSERT_OK_PTR(btf, "btf_new_empty"))
+ goto out;
+ btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
+ if (!ASSERT_OK(btf__load_into_kernel(btf), "btf_load"))
+ goto out;
+
+ fds[0] = map_fd;
+ fds[1] = btf__fd(btf);
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(f.gopts.insns);
+ attr.insn_cnt = f.gopts.insns_sz / sizeof(struct bpf_insn);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.fd_array = ptr_to_u64(fds);
+ attr.fd_array_cnt = 2;
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ ASSERT_EQ(prog_fd < 0 ? -errno : prog_fd, -EACCES,
+ "BTF in signed fd_array rejected");
+ if (prog_fd >= 0)
+ close(prog_fd);
+out:
+ if (btf)
+ btf__free(btf);
+ if (map_fd >= 0)
+ close(map_fd);
+ if (have_fixture)
+ gen_loader_fixture_fini(&f);
+ if (dir)
+ run_setup("cleanup", dir);
+ free(buf);
+}
+
+static void signature_failure_logs(void)
{
static const __u8 junk[64] = { 0x30, 0x42, 0x13, 0x37, };
+ char log_buf[1024] = {};
struct gen_loader_fixture f;
+ union bpf_attr attr;
int fd;
if (gen_loader_fixture_init(&f) == 0) {
/*
- * A present-but-invalid signature (the cert bytes are not a
- * PKCS#7 signature) must be rejected at load: the signature
- * path is honored, not ignored. (The valid path is covered by
- * the signed lskels.)
+ * Signature verification now runs inside bpf_check(), so a
+ * failure is reported through the verifier log. A present-but-
+ * invalid signature is rejected and the log says why.
*/
- fd = load_loader(f.gopts.insns, f.gopts.insns_sz, -1, junk,
- sizeof(junk), KEY_SPEC_SESSION_KEYRING);
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(f.gopts.insns);
+ attr.insn_cnt = f.gopts.insns_sz / sizeof(struct bpf_insn);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.signature = ptr_to_u64(junk);
+ attr.signature_size = sizeof(junk);
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ attr.log_level = 1;
+ attr.log_buf = ptr_to_u64(log_buf);
+ attr.log_size = sizeof(log_buf);
+ memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
+
+ fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
ASSERT_LT(fd, 0, "invalid signature rejected at load");
+ if (fd >= 0)
+ close(fd);
+ ASSERT_HAS_SUBSTR(log_buf, "signature verification failed",
+ "verifier logs signature failure");
}
gen_loader_fixture_fini(&f);
}
@@ -495,12 +573,31 @@ static void signature_too_large(void)
* is rejected before the buffer is read.
*/
fd = load_loader(f.gopts.insns, f.gopts.insns_sz, -1, junk,
- 64 << 20, KEY_SPEC_SESSION_KEYRING);
+ 64 << 20, KEY_SPEC_SESSION_KEYRING, 0);
ASSERT_EQ(fd, -EINVAL, "oversized signature rejected");
}
gen_loader_fixture_fini(&f);
}
+static void signature_zero_size(void)
+{
+ static const __u8 junk[64] = {};
+ struct gen_loader_fixture f;
+ int fd;
+
+ if (gen_loader_fixture_init(&f) == 0) {
+ /*
+ * A present signature with signature_size == 0 is rejected
+ * up front, before the keyring is resolved or the signature
+ * buffer is read.
+ */
+ fd = load_loader(f.gopts.insns, f.gopts.insns_sz, -1, junk,
+ 0, KEY_SPEC_SESSION_KEYRING, 0);
+ ASSERT_EQ(fd, -EINVAL, "zero-size signature rejected");
+ }
+ gen_loader_fixture_fini(&f);
+}
+
static void signature_bad_keyring(void)
{
static const __u8 junk[64] = {};
@@ -515,7 +612,7 @@ static void signature_bad_keyring(void)
* large positive serial takes the user-keyring path and won't exist.
*/
fd = load_loader(f.gopts.insns, f.gopts.insns_sz, -1, junk,
- sizeof(junk), INT_MAX);
+ sizeof(junk), INT_MAX, 0);
ASSERT_EQ(fd, -EINVAL, "signature with bad keyring_id rejected");
}
gen_loader_fixture_fini(&f);
@@ -575,7 +672,7 @@ static void metadata_ctx_max_entries_ignored(void)
memcpy(blob, gopts.data, data_sz);
r = run_gen_loader(gopts.insns, gopts.insns_sz, blob, data_sz,
- excl, sizeof(excl), NULL, 0, true, ctx, ctx_sz, &ran);
+ excl, sizeof(excl), NULL, 0, ctx, ctx_sz, &ran);
if (!ASSERT_TRUE(ran, "loader ran") ||
!ASSERT_EQ(r, 0, "loader retval"))
goto free_blob;
@@ -661,7 +758,7 @@ static void metadata_ctx_initial_value_ignored(void)
memcpy(blob, gopts.data, data_sz);
r = run_gen_loader(gopts.insns, gopts.insns_sz, blob, data_sz,
- excl, sizeof(excl), NULL, 0, true, ctx, ctx_sz, &ran);
+ excl, sizeof(excl), NULL, 0, ctx, ctx_sz, &ran);
if (!ASSERT_TRUE(ran, "loader ran") ||
!ASSERT_EQ(r, 0, "loader retval"))
goto free_blob;
@@ -714,6 +811,7 @@ static void signature_authenticates_insns(void)
__u8 excl[SHA256_DIGEST_LENGTH], sig[8192];
__u32 sig_sz = sizeof(sig), insns_sz, data_sz, ctx_sz;
unsigned char *insns = NULL, *tampered = NULL, *blob = NULL;
+ unsigned char *signbuf = NULL;
int nr_maps = 0, nr_progs = 0, r;
struct bpf_program *p;
struct bpf_map *m;
@@ -760,29 +858,141 @@ static void signature_authenticates_insns(void)
memcpy(blob, gopts.data, data_sz);
libbpf_sha256(insns, insns_sz, excl);
- if (!ASSERT_OK(sign_buf(dir, insns, insns_sz, sig, &sig_sz), "sign-file"))
+ signbuf = malloc((size_t)insns_sz + data_sz);
+ if (!ASSERT_OK_PTR(signbuf, "signbuf"))
+ goto cleanup;
+ memcpy(signbuf, insns, insns_sz);
+ memcpy(signbuf + insns_sz, blob, data_sz);
+ if (!ASSERT_OK(sign_buf(dir, signbuf, insns_sz + data_sz, sig, &sig_sz),
+ "sign-file"))
goto cleanup;
memset(ctx, 0, ctx_sz);
((struct bpf_loader_ctx *)ctx)->sz = ctx_sz;
r = run_gen_loader(insns, insns_sz, blob, data_sz, excl, sizeof(excl),
- sig, sig_sz, true, ctx, ctx_sz, &ran);
+ sig, sig_sz, ctx, ctx_sz, &ran);
ASSERT_TRUE(ran, "valid signature: loader loaded and ran");
ASSERT_EQ(r, 0, "valid signature accepted");
close_loader_ctx_fds(ctx, nr_maps, nr_progs);
memcpy(tampered, insns, insns_sz);
tampered[insns_sz / 2] ^= 0xff;
+ /*
+ * Bind the metadata map to the tampered loader's own digest, so the
+ * verifier's exclusive-map check (excl_prog_sha == prog->digest) passes
+ * and the signature - verified after the maps are resolved - is what
+ * rejects the load. This is the attacker's best case: even after
+ * re-binding the exclusive map to their tampered loader, the signature
+ * over the original insns || metadata still fails. (Leaving the map
+ * bound to the original digest would instead trip the excl check first.)
+ */
+ libbpf_sha256(tampered, insns_sz, excl);
memset(ctx, 0, ctx_sz);
((struct bpf_loader_ctx *)ctx)->sz = ctx_sz;
r = run_gen_loader(tampered, insns_sz, blob, data_sz, excl, sizeof(excl),
- sig, sig_sz, true, ctx, ctx_sz, &ran);
+ sig, sig_sz, ctx, ctx_sz, &ran);
ASSERT_FALSE(ran, "tampered loader rejected before run");
ASSERT_EQ(r, -EKEYREJECTED, "signature is bound to the instructions");
cleanup:
free(insns);
free(tampered);
free(blob);
+ free(signbuf);
+ free(ctx);
+ test_signed_loader__destroy(skel);
+ run_setup("cleanup", dir);
+}
+
+static void signature_authenticates_metadata(void)
+{
+ LIBBPF_OPTS(gen_loader_opts, gopts, .gen_hash = true);
+ char dir_tmpl[] = "/tmp/signed_loaderXXXXXX", *dir;
+ struct test_signed_loader *skel = NULL;
+ __u8 excl[SHA256_DIGEST_LENGTH], sig[8192];
+ __u32 sig_sz = sizeof(sig), insns_sz, data_sz, ctx_sz;
+ unsigned char *insns = NULL, *blob = NULL;
+ unsigned char *signbuf = NULL;
+ int nr_maps = 0, nr_progs = 0, r;
+ struct bpf_program *p;
+ struct bpf_map *m;
+ void *ctx = NULL;
+ bool ran;
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ return;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ return;
+ }
+
+ skel = test_signed_loader__open();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ goto cleanup;
+ if (!ASSERT_OK(bpf_object__gen_loader(skel->obj, &gopts), "gen_loader"))
+ goto cleanup;
+ if (!ASSERT_OK(bpf_object__load(skel->obj), "gen_load"))
+ goto cleanup;
+
+ bpf_object__for_each_program(p, skel->obj)
+ nr_progs++;
+ bpf_object__for_each_map(m, skel->obj)
+ nr_maps++;
+ ctx_sz = sizeof(struct bpf_loader_ctx) +
+ nr_maps * sizeof(struct bpf_map_desc) +
+ nr_progs * sizeof(struct bpf_prog_desc);
+ insns_sz = gopts.insns_sz;
+ data_sz = gopts.data_sz;
+ ctx = calloc(1, ctx_sz);
+ insns = malloc(insns_sz);
+ blob = malloc(data_sz);
+ if (!ASSERT_OK_PTR(ctx, "ctx") ||
+ !ASSERT_OK_PTR(insns, "insns") ||
+ !ASSERT_OK_PTR(blob, "blob"))
+ goto cleanup;
+ memcpy(insns, gopts.insns, insns_sz);
+ memcpy(blob, gopts.data, data_sz);
+ libbpf_sha256(insns, insns_sz, excl);
+
+ signbuf = malloc((size_t)insns_sz + data_sz);
+ if (!ASSERT_OK_PTR(signbuf, "signbuf"))
+ goto cleanup;
+ memcpy(signbuf, insns, insns_sz);
+ memcpy(signbuf + insns_sz, blob, data_sz);
+ if (!ASSERT_OK(sign_buf(dir, signbuf, insns_sz + data_sz, sig, &sig_sz),
+ "sign-file"))
+ goto cleanup;
+
+ memset(ctx, 0, ctx_sz);
+ ((struct bpf_loader_ctx *)ctx)->sz = ctx_sz;
+ r = run_gen_loader(insns, insns_sz, blob, data_sz, excl, sizeof(excl),
+ sig, sig_sz, ctx, ctx_sz, &ran);
+ ASSERT_TRUE(ran, "valid signature: loader loaded and ran");
+ ASSERT_EQ(r, 0, "valid signature accepted");
+ close_loader_ctx_fds(ctx, nr_maps, nr_progs);
+
+ /*
+ * Tamper the metadata after signing while leaving the instructions
+ * and thus the exclusive hash binding untouched: the map freezes
+ * fine and excl_prog_sha still matches the loader's digest, so the
+ * load reaches signature verification, which folds the live frozen
+ * map bytes into the checked payload and must reject the modified
+ * blob. A kernel folding anything but the map contents themselves
+ * would wrongly accept this load.
+ */
+ blob[data_sz / 2] ^= 0xff;
+ memset(ctx, 0, ctx_sz);
+ ((struct bpf_loader_ctx *)ctx)->sz = ctx_sz;
+ r = run_gen_loader(insns, insns_sz, blob, data_sz, excl, sizeof(excl),
+ sig, sig_sz, ctx, ctx_sz, &ran);
+ ASSERT_FALSE(ran, "tampered metadata rejected before run");
+ ASSERT_EQ(r, -EKEYREJECTED, "signature is bound to the metadata");
+cleanup:
+ free(insns);
+ free(blob);
+ free(signbuf);
free(ctx);
test_signed_loader__destroy(skel);
run_setup("cleanup", dir);
@@ -1007,10 +1217,11 @@ static void lsm_signature_verdict(void)
{
char dir_tmpl[] = "/tmp/signed_loader_lsmXXXXXX", *dir = NULL;
struct test_signed_loader_lsm *lsm = NULL;
+ __u32 sig_sz = 8192, msig_sz = 8192;
int map_fd = -1, prog_fd = -1;
bool have_fixture = false;
struct gen_loader_fixture f;
- __u32 sig_sz = 8192;
+ unsigned char *buf;
__s32 ses_serial;
__u8 sig[8192];
@@ -1029,7 +1240,7 @@ static void lsm_signature_verdict(void)
if (!ASSERT_OK_FD(map_fd, "meta_map_unsigned"))
goto out;
lsm->bss->seen = 0;
- prog_fd = load_loader(f.gopts.insns, f.gopts.insns_sz, map_fd, NULL, 0, 0);
+ prog_fd = load_loader(f.gopts.insns, f.gopts.insns_sz, map_fd, NULL, 0, 0, 0);
close(map_fd);
map_fd = -1;
if (!ASSERT_OK_FD(prog_fd, "unsigned loader load"))
@@ -1062,22 +1273,51 @@ static void lsm_signature_verdict(void)
goto out;
lsm->bss->seen = 0;
prog_fd = load_loader(f.gopts.insns, f.gopts.insns_sz, map_fd, sig,
- sig_sz, KEY_SPEC_SESSION_KEYRING);
+ sig_sz, KEY_SPEC_SESSION_KEYRING, 0);
close(map_fd);
map_fd = -1;
- if (!ASSERT_OK_FD(prog_fd, "signed loader load"))
- goto out;
- close(prog_fd);
+ ASSERT_EQ(prog_fd, -EACCES, "unfolded metadata rejected");
+ if (prog_fd >= 0)
+ close(prog_fd);
prog_fd = -1;
ses_serial = syscall(__NR_keyctl, KEYCTL_GET_KEYRING_ID,
KEY_SPEC_SESSION_KEYRING, 0);
ASSERT_EQ(lsm->bss->seen, 1, "signed: one observed load");
- ASSERT_EQ(lsm->bss->sig_verdict, BPF_SIG_VERIFIED, "signed verdict");
+ ASSERT_EQ(lsm->bss->sig_verdict, BPF_SIG_VERIFIED,
+ "admission saw a valid signature");
ASSERT_EQ(lsm->bss->sig_keyring_type, BPF_SIG_KEYRING_USER, "signed keyring type");
ASSERT_GT(ses_serial, 0, "session keyring serial resolved");
ASSERT_EQ(lsm->bss->sig_keyring_serial, ses_serial,
"signed: validated against session keyring");
+
+ buf = malloc((size_t)f.gopts.insns_sz + f.data_sz);
+ if (!ASSERT_OK_PTR(buf, "meta_signbuf"))
+ goto out;
+ memcpy(buf, f.gopts.insns, f.gopts.insns_sz);
+ memcpy(buf + f.gopts.insns_sz, f.blob, f.data_sz);
+ if (!ASSERT_OK(sign_buf(dir, buf, f.gopts.insns_sz + f.data_sz,
+ sig, &msig_sz), "sign insns||metadata")) {
+ free(buf);
+ goto out;
+ }
+ free(buf);
+
+ map_fd = setup_meta_map(&f);
+ if (!ASSERT_OK_FD(map_fd, "meta_map_bound"))
+ goto out;
+ lsm->bss->seen = 0;
+ prog_fd = load_loader(f.gopts.insns, f.gopts.insns_sz, map_fd, sig,
+ msig_sz, KEY_SPEC_SESSION_KEYRING, 1);
+ close(map_fd);
+ map_fd = -1;
+ if (!ASSERT_OK_FD(prog_fd, "metadata-bound loader load"))
+ goto out;
+ close(prog_fd);
+ prog_fd = -1;
+ ASSERT_EQ(lsm->bss->seen, 1, "metadata: one observed load");
+ ASSERT_EQ(lsm->bss->sig_verdict, BPF_SIG_VERIFIED,
+ "metadata-bound verdict");
out:
if (map_fd >= 0)
close(map_fd);
@@ -1090,22 +1330,471 @@ static void lsm_signature_verdict(void)
test_signed_loader_lsm__destroy(lsm);
}
+/*
+ * Load-time metadata verification: the kernel folds the frozen metadata map
+ * into the signature (insns || metadata) and checks it at BPF_PROG_LOAD via
+ * fd_array_cnt, rather than the loader checking from within BPF. Sign that
+ * concatenation, hand the kernel the map, and confirm the signed loader loads,
+ * runs, and installs its target.
+ */
+static int loadtime_drive(const char *dir, const void *insns, __u32 insns_sz,
+ const void *data, __u32 data_sz, const __u8 *excl,
+ void *ctx, __u32 ctx_sz, int *load_ret, bool *ran)
+{
+ LIBBPF_OPTS(bpf_map_create_opts, mopts,
+ .excl_prog_hash = excl,
+ .excl_prog_hash_size = SHA256_DIGEST_LENGTH);
+ __u32 sig_sz = 8192, key = 0;
+ unsigned char *buf = NULL;
+ int map_fd, prog_fd, ret = 0;
+ union bpf_attr attr;
+ __u8 sig[8192];
+
+ *ran = false;
+ *load_ret = 0;
+
+ /*
+ * Metadata map, bound to the loader digest and frozen, exactly as
+ * skel_internal.h's bpf_load_and_run() sets it up.
+ */
+ map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "__loader.map", 4,
+ data_sz, 1, &mopts);
+ if (map_fd < 0) {
+ ret = -errno;
+ goto out_load;
+ }
+ if (bpf_map_update_elem(map_fd, &key, data, 0) || bpf_map_freeze(map_fd)) {
+ ret = -errno;
+ goto out_load;
+ }
+
+ /* Sign insns || metadata, the same bytes the kernel reconstructs. */
+ buf = malloc((size_t)insns_sz + data_sz);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out_load;
+ }
+ memcpy(buf, insns, insns_sz);
+ memcpy(buf + insns_sz, data, data_sz);
+ ret = sign_buf(dir, buf, insns_sz + data_sz, sig, &sig_sz);
+ if (ret)
+ goto out_load;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(insns);
+ attr.insn_cnt = insns_sz / sizeof(struct bpf_insn);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.fd_array = ptr_to_u64(&map_fd);
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ attr.fd_array_cnt = 1;
+ memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ if (prog_fd < 0) {
+ ret = -errno;
+ goto out_load;
+ }
+
+ memset(&attr, 0, sizeof(attr));
+ attr.test.prog_fd = prog_fd;
+ attr.test.ctx_in = ptr_to_u64(ctx);
+ attr.test.ctx_size_in = ctx_sz;
+ if (syscall(__NR_bpf, BPF_PROG_RUN, &attr,
+ offsetofend(union bpf_attr, test)) < 0) {
+ ret = -errno;
+ goto out_prog;
+ }
+ *ran = true;
+ ret = (int)attr.test.retval;
+out_prog:
+ close(prog_fd);
+ goto out_map;
+out_load:
+ *load_ret = ret;
+out_map:
+ free(buf);
+ if (map_fd >= 0)
+ close(map_fd);
+ return ret;
+}
+
+static void loadtime_verify(struct bpf_object *obj, int expect_maps)
+{
+ LIBBPF_OPTS(gen_loader_opts, gopts, .gen_hash = true);
+ char dir_tmpl[] = "/tmp/signed_loader_ltXXXXXX", *dir = NULL;
+ int nr_maps = 0, nr_progs = 0, load_ret = 0, r;
+ __u8 excl[SHA256_DIGEST_LENGTH];
+ struct bpf_prog_desc *pd;
+ struct bpf_map_desc *md;
+ unsigned char *blob = NULL;
+ struct bpf_program *p;
+ struct bpf_map *m;
+ __u32 ctx_sz, data_sz;
+ void *ctx = NULL;
+ bool ran = false;
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ return;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ return;
+ }
+
+ if (!ASSERT_OK(bpf_object__gen_loader(obj, &gopts), "gen_loader"))
+ goto out;
+ if (!ASSERT_OK(bpf_object__load(obj), "gen_load"))
+ goto out;
+
+ bpf_object__for_each_program(p, obj)
+ nr_progs++;
+ bpf_object__for_each_map(m, obj)
+ nr_maps++;
+ if (!ASSERT_EQ(nr_maps, expect_maps, "fixture map count"))
+ goto out;
+
+ ctx_sz = sizeof(struct bpf_loader_ctx) +
+ nr_maps * sizeof(struct bpf_map_desc) +
+ nr_progs * sizeof(struct bpf_prog_desc);
+ ctx = calloc(1, ctx_sz);
+ if (!ASSERT_OK_PTR(ctx, "ctx_alloc"))
+ goto out;
+ ((struct bpf_loader_ctx *)ctx)->sz = ctx_sz;
+
+ data_sz = gopts.data_sz;
+ blob = malloc(data_sz);
+ if (!ASSERT_OK_PTR(blob, "blob_alloc"))
+ goto out;
+ memcpy(blob, gopts.data, data_sz);
+
+ /* excl_prog_hash = SHA256(loader insns) == the loader's prog->digest. */
+ libbpf_sha256(gopts.insns, gopts.insns_sz, excl);
+
+ r = loadtime_drive(dir, gopts.insns, gopts.insns_sz, blob, data_sz,
+ excl, ctx, ctx_sz, &load_ret, &ran);
+ ASSERT_OK(load_ret, "signed loader loaded (insns || metadata)");
+ ASSERT_TRUE(ran, "loader ran");
+ ASSERT_EQ(r, 0, "loader installed its target");
+
+ md = (struct bpf_map_desc *)((char *)ctx + sizeof(struct bpf_loader_ctx));
+ pd = (struct bpf_prog_desc *)(md + nr_maps);
+ ASSERT_GT(pd[0].prog_fd, 0, "target program installed");
+ if (nr_maps)
+ ASSERT_GT(md[0].map_fd, 0, "target map installed");
+
+ close_loader_ctx_fds(ctx, nr_maps, nr_progs);
+out:
+ free(blob);
+ free(ctx);
+ if (dir)
+ run_setup("cleanup", dir);
+}
+
+static void loadtime_no_map(void)
+{
+ struct test_signed_loader *skel = test_signed_loader__open();
+
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+ loadtime_verify(skel->obj, 0);
+ test_signed_loader__destroy(skel);
+}
+
+static void loadtime_with_map(void)
+{
+ struct test_signed_loader_map *skel = test_signed_loader_map__open();
+
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+ loadtime_verify(skel->obj, 1);
+ test_signed_loader_map__destroy(skel);
+}
+
+/*
+ * A signed program need not bind any map. A plain BPF_PROG_TYPE_SYSCALL
+ * program with no fd_array is signed over its instructions alone: the kernel
+ * verifies the signature, folds no metadata, and the program loads. Exercise
+ * the fd_array == NULL / fd_array_cnt == 0 path, and confirm the signature
+ * still authenticates the instructions (a tampered copy is rejected).
+ */
+static void signed_no_fd_array(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ char dir_tmpl[] = "/tmp/signed_loaderXXXXXX", *dir;
+ __u32 sig_sz = 8192;
+ union bpf_attr attr;
+ __u8 sig[8192];
+ int prog_fd, err;
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ return;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ return;
+ }
+
+ /* No metadata map: the signed payload is the instructions alone. */
+ if (!ASSERT_OK(sign_buf(dir, insns, sizeof(insns), sig, &sig_sz),
+ "sign-file"))
+ goto cleanup;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(insns);
+ attr.insn_cnt = ARRAY_SIZE(insns);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ /* fd_array and fd_array_cnt deliberately left NULL/0. */
+ memcpy(attr.prog_name, "signed_nomap", sizeof("signed_nomap"));
+
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ if (!ASSERT_GE(prog_fd, 0, "map-less signed program loaded")) {
+ if (prog_fd >= 0)
+ close(prog_fd);
+ goto cleanup;
+ }
+ close(prog_fd);
+
+ /* The signature covers the instructions, so tampering must be rejected. */
+ insns[0].imm = 1;
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ err = prog_fd < 0 ? -errno : prog_fd;
+ ASSERT_EQ(err, -EKEYREJECTED, "tampered map-less program rejected");
+ if (prog_fd >= 0)
+ close(prog_fd);
+cleanup:
+ run_setup("cleanup", dir);
+}
+
+/*
+ * A signed program may reach maps only through fd_array indices, so the kernel
+ * folds (and thus attests) them. A direct BPF_PSEUDO_MAP_FD reference - a raw,
+ * unfolded fd baked into the signed instructions - is rejected by the verifier.
+ */
+static void signed_map_by_fd_rejected(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ char dir_tmpl[] = "/tmp/signed_loaderXXXXXX", *dir;
+ __u32 sig_sz = 8192;
+ union bpf_attr attr;
+ __u8 sig[8192];
+ int map_fd, prog_fd, err;
+
+ map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "sig_mapfd", 4, 4, 1, NULL);
+ if (!ASSERT_GE(map_fd, 0, "map_create"))
+ return;
+ insns[0].imm = map_fd; /* bake the raw map fd into the ld_imm64 */
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ goto out_map;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ goto out_map;
+ }
+
+ /* Sign the instructions, raw map fd and all. */
+ if (!ASSERT_OK(sign_buf(dir, insns, sizeof(insns), sig, &sig_sz),
+ "sign-file"))
+ goto cleanup;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(insns);
+ attr.insn_cnt = ARRAY_SIZE(insns);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ /* No fd_array: the map is reached by a raw fd in the instructions. */
+ memcpy(attr.prog_name, "signed_mapfd", sizeof("signed_mapfd"));
+
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ err = prog_fd < 0 ? -errno : prog_fd;
+ ASSERT_EQ(err, -EINVAL, "signed program referencing a map by fd rejected");
+ if (prog_fd >= 0)
+ close(prog_fd);
+cleanup:
+ run_setup("cleanup", dir);
+out_map:
+ close(map_fd);
+}
+
+/*
+ * A signed program may reach maps only through the continuous fd_array, so the
+ * kernel folds (and thus attests) them. Referencing a map by fd_array *index*
+ * while leaving fd_array_cnt at 0 selects the sparse path, which resolves a map
+ * the signature never covered; the verifier rejects it up front with -EACCES.
+ */
+static void signed_sparse_fd_array_rejected(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_LD_IMM64_RAW(BPF_REG_1, BPF_PSEUDO_MAP_IDX, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ char dir_tmpl[] = "/tmp/signed_loader_spXXXXXX", *dir;
+ __u32 sig_sz = 8192;
+ union bpf_attr attr;
+ __u8 sig[8192];
+ int map_fd, prog_fd, err;
+
+ map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "sig_sparse", 4, 4, 1, NULL);
+ if (!ASSERT_GE(map_fd, 0, "map_create"))
+ return;
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ goto out_map;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ goto out_map;
+ }
+
+ /* Sign the instructions alone; the sparse map is not folded. */
+ if (!ASSERT_OK(sign_buf(dir, insns, sizeof(insns), sig, &sig_sz),
+ "sign-file"))
+ goto cleanup;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(insns);
+ attr.insn_cnt = ARRAY_SIZE(insns);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.fd_array = ptr_to_u64(&map_fd);
+ attr.fd_array_cnt = 0; /* sparse: force lazy map resolution */
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ memcpy(attr.prog_name, "signed_sparse", sizeof("signed_sparse"));
+
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ err = prog_fd < 0 ? -errno : prog_fd;
+ ASSERT_EQ(err, -EACCES, "signed program binding a sparse fd_array map rejected");
+ if (prog_fd >= 0)
+ close(prog_fd);
+cleanup:
+ run_setup("cleanup", dir);
+out_map:
+ close(map_fd);
+}
+
+static void signed_module_kfunc_rejected(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 1, 1),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ char dir_tmpl[] = "/tmp/signed_loader_kfnXXXXXX", *dir;
+ int prog_fd, err, fds[2];
+ struct btf *btf = NULL;
+ __u32 sig_sz = 8192;
+ union bpf_attr attr;
+ __u8 sig[8192];
+
+ syscall(__NR_request_key, "keyring", "_uid.0", NULL,
+ KEY_SPEC_SESSION_KEYRING);
+ dir = mkdtemp(dir_tmpl);
+ if (!ASSERT_OK_PTR(dir, "mkdtemp"))
+ return;
+ if (!ASSERT_OK(run_setup("setup", dir), "verify_sig_setup")) {
+ rmdir(dir);
+ return;
+ }
+ if (!ASSERT_OK(sign_buf(dir, insns, sizeof(insns), sig, &sig_sz),
+ "sign-file"))
+ goto cleanup;
+ btf = btf__new_empty();
+ if (!ASSERT_OK_PTR(btf, "btf_new_empty"))
+ goto cleanup;
+ btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
+ if (!ASSERT_OK(btf__load_into_kernel(btf), "btf_load"))
+ goto cleanup;
+ fds[0] = -1;
+ fds[1] = btf__fd(btf);
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SYSCALL;
+ attr.insns = ptr_to_u64(insns);
+ attr.insn_cnt = ARRAY_SIZE(insns);
+ attr.license = ptr_to_u64("Dual BSD/GPL");
+ attr.prog_flags = BPF_F_SLEEPABLE;
+ attr.fd_array = ptr_to_u64(fds);
+ attr.fd_array_cnt = 0; /* sparse: force lazy kfunc BTF resolution */
+ attr.signature = ptr_to_u64(sig);
+ attr.signature_size = sig_sz;
+ attr.keyring_id = KEY_SPEC_SESSION_KEYRING;
+ memcpy(attr.prog_name, "signed_kfunc", sizeof("signed_kfunc"));
+
+ prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr,
+ offsetofend(union bpf_attr, keyring_id));
+ err = prog_fd < 0 ? -errno : prog_fd;
+ if (prog_fd >= 0)
+ close(prog_fd);
+
+ ASSERT_EQ(err, -EACCES, "module kfunc BTF in signed program rejected");
+cleanup:
+ if (btf)
+ btf__free(btf);
+ run_setup("cleanup", dir);
+}
+
void test_signed_loader(void)
{
- if (test__start_subtest("metadata_check_shape"))
- metadata_check_shape();
+ if (test__start_subtest("loadtime_no_map"))
+ loadtime_no_map();
+ if (test__start_subtest("loadtime_with_map"))
+ loadtime_with_map();
if (test__start_subtest("metadata_match"))
metadata_match();
- if (test__start_subtest("metadata_sha_mismatch"))
- metadata_sha_mismatch();
- if (test__start_subtest("metadata_not_exclusive"))
- metadata_not_exclusive();
- if (test__start_subtest("metadata_hash_not_computed"))
- metadata_hash_not_computed();
if (test__start_subtest("signature_enforced"))
signature_enforced();
+ if (test__start_subtest("signed_nonexcl_fd_array_rejected"))
+ signed_nonexcl_fd_array_rejected();
+ if (test__start_subtest("signed_unfrozen_fd_array_rejected"))
+ signed_unfrozen_fd_array_rejected();
+ if (test__start_subtest("signed_nonarray_fd_array_rejected"))
+ signed_nonarray_fd_array_rejected();
+ if (test__start_subtest("signed_btf_fd_array_rejected"))
+ signed_btf_fd_array_rejected();
+ if (test__start_subtest("signed_module_kfunc_rejected"))
+ signed_module_kfunc_rejected();
+ if (test__start_subtest("signature_failure_logs"))
+ signature_failure_logs();
if (test__start_subtest("signature_too_large"))
signature_too_large();
+ if (test__start_subtest("signature_zero_size"))
+ signature_zero_size();
if (test__start_subtest("signature_bad_keyring"))
signature_bad_keyring();
if (test__start_subtest("metadata_ctx_max_entries_ignored"))
@@ -1114,6 +1803,8 @@ void test_signed_loader(void)
metadata_ctx_initial_value_ignored();
if (test__start_subtest("signature_authenticates_insns"))
signature_authenticates_insns();
+ if (test__start_subtest("signature_authenticates_metadata"))
+ signature_authenticates_metadata();
if (test__start_subtest("hash_requires_frozen"))
hash_requires_frozen();
if (test__start_subtest("no_update_after_freeze"))
@@ -1132,4 +1823,10 @@ void test_signed_loader(void)
map_hash_unsupported_type();
if (test__start_subtest("lsm_signature_verdict"))
lsm_signature_verdict();
+ if (test__start_subtest("signed_no_fd_array"))
+ signed_no_fd_array();
+ if (test__start_subtest("signed_map_by_fd_rejected"))
+ signed_map_by_fd_rejected();
+ if (test__start_subtest("signed_sparse_fd_array_rejected"))
+ signed_sparse_fd_array_rejected();
}
diff --git a/tools/testing/selftests/bpf/progs/test_signed_loader.c b/tools/testing/selftests/bpf/progs/test_signed_loader.c
index d9a4b85f9391..50451a69b99a 100644
--- a/tools/testing/selftests/bpf/progs/test_signed_loader.c
+++ b/tools/testing/selftests/bpf/progs/test_signed_loader.c
@@ -4,10 +4,11 @@
/*
* Minimal, map-less program. Driven through libbpf's gen_loader (gen_hash)
- * by prog_tests/signed_loader.c so the generated light-skeleton loader (with
- * the emit_signature_match metadata check) can be exercised against good
- * and tampered metadata. A socket filter needs no load-time attach resolution,
- * and having no maps keeps the generated loader's ctx trivial (0 maps, 1 prog).
+ * by prog_tests/signed_loader.c so the generated light-skeleton loader can be
+ * exercised against good and tampered metadata, which the kernel now verifies
+ * at load time via the insns||metadata signature. A socket filter needs no
+ * load-time attach resolution, and having no maps keeps the generated loader's
+ * ctx trivial (0 maps, 1 prog).
*/
SEC("socket")
int probe(void *ctx)
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 6/8] selftests/bpf: Adjust bpf_map layout in verifier_map_ptr
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
With write-only excl member removed from struct bpf_map, ops moves
to offset 32 and inner_map_meta to offset 40. Update the expected
verifier message for the former and retarget the latter at the sha
byte array, so the beyond-member-end rejection path stays covered:
# LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t verifier_map_ptr
[...]
#619/5 verifier_map_ptr/bpf_map_ptr: read non-existent field rejected:OK
#619/6 verifier_map_ptr/bpf_map_ptr: read non-existent field rejected @unpriv:OK
#619/7 verifier_map_ptr/bpf_map_ptr: read beyond sha field rejected:OK
#619/8 verifier_map_ptr/bpf_map_ptr: read beyond sha field rejected @unpriv:OK
#619/9 verifier_map_ptr/bpf_map_ptr: read ops field accepted:OK
#619/10 verifier_map_ptr/bpf_map_ptr: read ops field accepted @unpriv:OK
[...]
#620 verifier_map_ptr_mixing:OK
Summary: 2/20 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
.../selftests/bpf/progs/verifier_map_ptr.c | 23 ++++++++++---------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/verifier_map_ptr.c b/tools/testing/selftests/bpf/progs/verifier_map_ptr.c
index 166193659870..e0a65835c861 100644
--- a/tools/testing/selftests/bpf/progs/verifier_map_ptr.c
+++ b/tools/testing/selftests/bpf/progs/verifier_map_ptr.c
@@ -72,14 +72,15 @@ __naked void bpf_map_ptr_write_rejected(void)
/*
* struct bpf_map starts with the SHA256 hash sha[32] at offset 0 (a readable
- * byte array), the u32 excl field at offset 32, and the ops pointer at offset
- * 40. Reading a u32 at offset 41 reaches into the middle of the ops pointer,
- * i.e. a partial pointer access, which is rejected.
+ * byte array), followed by the ops pointer at offset 32 and the inner_map_meta
+ * pointer at offset 40. Reading a u32 at offset 41 reaches into the middle of
+ * the inner_map_meta pointer, i.e. a partial pointer access, which is
+ * rejected.
*/
SEC("socket")
__description("bpf_map_ptr: read non-existent field rejected")
__failure
-__msg("cannot access ptr member ops with moff 40 in struct bpf_map with off 41 size 4")
+__msg("cannot access ptr member inner_map_meta with moff 40 in struct bpf_map with off 41 size 4")
__failure_unpriv
__msg_unpriv("access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN")
__flag(BPF_F_ANY_ALIGNMENT)
@@ -97,23 +98,23 @@ __naked void read_non_existent_field_rejected(void)
}
/*
- * The u32 excl field spans offsets 32..35 (mend 36). Reading a u32 at offset
- * 33 starts inside excl but extends past its end, which the verifier rejects
+ * The sha byte array spans offsets 0..31 (mend 32). Reading a u32 at offset
+ * 30 starts inside sha but extends past its end, which the verifier rejects
* as an out-of-bounds scalar access.
*/
SEC("socket")
-__description("bpf_map_ptr: read beyond excl field rejected")
+__description("bpf_map_ptr: read beyond sha field rejected")
__failure
-__msg("access beyond the end of member excl (mend:36) in struct bpf_map with off 33 size 4")
+__msg("access beyond the end of member sha (mend:32) in struct bpf_map with off 30 size 4")
__failure_unpriv
__msg_unpriv("access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN")
__flag(BPF_F_ANY_ALIGNMENT)
-__naked void read_beyond_excl_field_rejected(void)
+__naked void read_beyond_sha_field_rejected(void)
{
asm volatile (" \
r6 = 0; \
r1 = %[map_array_48b] ll; \
- r6 = *(u32*)(r1 + 33); \
+ r6 = *(u32*)(r1 + 30); \
r0 = 1; \
exit; \
" :
@@ -131,7 +132,7 @@ __naked void ptr_read_ops_field_accepted(void)
asm volatile (" \
r6 = 0; \
r1 = %[map_array_48b] ll; \
- r6 = *(u64*)(r1 + 40); \
+ r6 = *(u64*)(r1 + 32); \
r0 = 1; \
exit; \
" :
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 2/8] bpf: Verify signed loader metadata at load time
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
A signed gen_loader program carries the programs, maps and relocations
it installs in a metadata array map. The loader instructions are covered
by the PKCS#7 signature, but the metadata map is not: Today the loader
compares the map contents from within BPF against a hash baked into its
(signed) instructions, using the kernel-cached map hash. The kernel
itself never actually attests that the metadata the loader installs is
the metadata that was signed.
This split is the core of the long-standing objection to the BPF signing
scheme from the LSM / integrity side: the integrity check of a light
skeleton only completes once the loader program runs, that is, after the
security_bpf_prog_load() hook, so at admission time an LSM observes a
program whose payload has not yet been verified. Auditing the chain
link is also not a purely cryptographic operation: whoever signs or
reviews an lskel has to disassemble the loader's preamble to convince
themselves that the embedded hash check is present and correct [0][1].
Two acceptable fixes were identified in those threads: Complete the
integrity check before the admission hook fires, or add a second hook
that collects the verification result after the loader ran [2]. Covering
both the loader and its maps directly with the PKCS#7 signature is what
Blaise Boscaccy's patchsets proposed in several forms. Let's implement
the former, without growing the UAPI, and in particular as a single
unified scheme where the signature spans the raw bytes rather than
derived hashes.
A signed loader binds its metadata map(s) through the existing fd_array,
and an exclusive map is already bound to a program digest (excl_prog_hash).
So when a signature is present, collect the exclusive maps from fd_array
and append their frozen contents to the instructions before verification:
The signature now covers insns || metadata_0 || metadata_1 || [...] in
the fd_array order, and verification completes in bpf_check(), once the
fd_array maps are resolved into used_maps, before the LSM admission hook
and the rest of verification. A program is either BPF_SIG_UNSIGNED or
BPF_SIG_VERIFIED, with nothing in between. While folding the fd_array
maps, a non-exclusive map bound to a signed program is rejected, so every
map folded into the signature is exclusive. A signed loader that fails
to cover its metadata thus does not load, and BPF_SIG_VERIFIED always
means the instructions and every exclusive map are authentic. The maps
must be frozen so the hashed bytes cannot change before the loader runs;
the map <-> program digest binding is enforced by the verifier for every
used map. Binding maps through fd_array_cnt makes the verifier resolve
and excl-check them (excl_prog_sha vs prog->digest) before it would
otherwise compute the digest, so compute prog->digest up front in
bpf_check(), over the unmodified instructions the signature covers, for
a load that folds metadata.
Unsigned programs are not affected by the signature path; for them the
LSM admission hook merely moves below fd_array resolution, with minimal
bounded work in between. Note, signed loaders generated by older libbpf/
bpftool versions need to be regenerated; some of the recent fixes we've
had on the signed loader side require the latter already to close gaps.
Finally, some remarks around the security_bpf_prog_load() placement
given there was discussion on whether a new hook is needed or the existing
security_bpf_prog() hook should be reused [3]: For a new hook it would
mean that just for loading a single BPF program it has to pass through
four layers of LSM hooks:
1) security_bpf (cmd=PROG_LOAD): for gating various bpf subcmds
2) security_bpf_prog_load: historical admission hook (CAP/token,
prog_type, attach point), pre-verification
3) security_bpf_prog_verify_signature: newly asked admission hook,
same role as 2), plus the BPF signature verdict
4) security_bpf_prog: gate handing the prog fd back to userspace,
verification done & signature verified
The use-cases of 2) and 3) conflate, thus BPF community prefers to just
keep a total of 3 LSM hooks (as-is today): 3) makes 2) incoherent given
they are the /same class/ of hook, that is, access-control admission on
the load and split only by _what_ they can see. Worse, with the split,
for a signed BPF program security_bpf_prog_load 2) admits a program whose
signature has not been checked, so a policy gating at 2) is structurally
unable to express "admit only verified" and every such policy is forced
onto 3) *anyway*. In other words, one doesn't get two complementary hooks,
but rather, one real admission hook aka 3) plus a now-degraded /legacy/
hook 2) that can't answer the question operators actually want to ask.
Reusing security_bpf_prog() 4) for admission is no alternative either:
it fires only after the entire verifier (and JIT) pipeline ran, so
denying a not-yet-verified program at that point burns exactly the
work a denial is supposed to avoid, and by then the program has an id
assigned and the kallsyms/perf/audit load events fired. Policies are
free to also consume the signature verdict at 4), but admission control
belongs into security_bpf_prog_load(). Hence the latter remains the only
admission hook, merely moved past signature verification; with moving
large allocations further down into the BPF verifier, there is now only
minimal work between the old and new location: The preparation work in
bpf_check() is reordered such that only the minimally necessary setup
happens up front: Allocating the env, initializing the verifier log and
resolving the fd_array that a signed BPF metadata map needs. The worst
case allocation up until security_bpf_prog_load() is ~90K which is the
env itself (~54K) plus the continuous fd_array cache (at most 32K). The
insn_aux_data array is moved into a later stage in the verification.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/2f71d6c03698eb17d51f7247efde777627ee578a.camel@HansenPartnership.com [0]
Link: https://lore.kernel.org/lkml/ecf0521ed302db672672ebfbc670ecfba36a6e00.camel@HansenPartnership.com [1]
Link: https://lore.kernel.org/bpf/88703f00d5b7a779728451008626efa45e42db3d.camel@HansenPartnership.com [2]
Link: https://lore.kernel.org/bpf/DJOFY21DYUI4.19WKQ3NPZ4H5R@gmail.com [3]
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/syscall.c | 76 +-----------
kernel/bpf/verifier.c | 234 +++++++++++++++++++++++++++++++----
3 files changed, 215 insertions(+), 96 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index bb57773cde37..317e99b9acc0 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -947,6 +947,7 @@ struct bpf_verifier_env {
bool bypass_spec_v4;
bool seen_direct_write;
bool seen_exception;
+ bool signature;
struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
const struct bpf_line_info *prev_linfo;
struct bpf_verifier_log log;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6db306d23b47..e898fad01aaf 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -40,7 +40,6 @@
#include <linux/tracepoint.h>
#include <linux/overflow.h>
#include <linux/cookie.h>
-#include <linux/verification.h>
#include <linux/btf_ids.h>
#include <net/netfilter/nf_bpf_link.h>
@@ -2886,64 +2885,6 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
}
}
-static enum bpf_sig_keyring bpf_classify_keyring(s32 keyring_id)
-{
- switch (keyring_id) {
- case 0:
- return BPF_SIG_KEYRING_BUILTIN;
- case (s32)(unsigned long)VERIFY_USE_SECONDARY_KEYRING:
- return BPF_SIG_KEYRING_SECONDARY;
- case (s32)(unsigned long)VERIFY_USE_PLATFORM_KEYRING:
- return BPF_SIG_KEYRING_PLATFORM;
- default:
- return BPF_SIG_KEYRING_USER;
- }
-}
-
-static int bpf_prog_verify_signature(struct bpf_prog *prog, union bpf_attr *attr,
- bool is_kernel, s32 *keyring_serial)
-{
- bpfptr_t usig = make_bpfptr(attr->signature, is_kernel);
- struct bpf_dynptr_kern sig_ptr, insns_ptr;
- struct bpf_key *key = NULL;
- void *sig;
- int err = 0;
-
- /*
- * Don't attempt to use kmalloc_large or vmalloc for signatures.
- * Practical signature for BPF program should be below this limit.
- */
- if (attr->signature_size > KMALLOC_MAX_CACHE_SIZE)
- return -EINVAL;
-
- if (system_keyring_id_check(attr->keyring_id) == 0)
- key = bpf_lookup_system_key(attr->keyring_id);
- else
- key = bpf_lookup_user_key(attr->keyring_id, 0);
-
- if (!key)
- return -EINVAL;
-
- sig = kvmemdup_bpfptr(usig, attr->signature_size);
- if (IS_ERR(sig)) {
- bpf_key_put(key);
- return PTR_ERR(sig);
- }
-
- bpf_dynptr_init(&sig_ptr, sig, BPF_DYNPTR_TYPE_LOCAL, 0,
- attr->signature_size);
- bpf_dynptr_init(&insns_ptr, prog->insnsi, BPF_DYNPTR_TYPE_LOCAL, 0,
- prog->len * sizeof(struct bpf_insn));
-
- err = bpf_verify_pkcs7_signature((struct bpf_dynptr *)&insns_ptr,
- (struct bpf_dynptr *)&sig_ptr, key);
- if (!err)
- *keyring_serial = bpf_key_serial(key);
- bpf_key_put(key);
- kvfree(sig);
- return err;
-}
-
static int bpf_prog_mark_insn_arrays_ready(struct bpf_prog *prog)
{
int err;
@@ -3133,17 +3074,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_at
/* eBPF programs must be GPL compatible to use GPL-ed functions */
prog->gpl_compatible = license_is_gpl_compatible(license) ? 1 : 0;
- if (attr->signature) {
- err = bpf_prog_verify_signature(prog, attr, uattr.is_kernel,
- &prog->aux->sig.keyring_serial);
- if (err)
- goto free_prog;
- prog->aux->sig.keyring_type = bpf_classify_keyring(attr->keyring_id);
- prog->aux->sig.verdict = BPF_SIG_VERIFIED;
- } else {
- prog->aux->sig.keyring_type = BPF_SIG_KEYRING_NONE;
- prog->aux->sig.verdict = BPF_SIG_UNSIGNED;
- }
+ prog->aux->sig.keyring_type = BPF_SIG_KEYRING_NONE;
+ prog->aux->sig.verdict = BPF_SIG_UNSIGNED;
prog->orig_prog = NULL;
prog->jited = 0;
@@ -3189,10 +3121,6 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_at
if (err < 0)
goto free_prog;
- err = security_bpf_prog_load(prog, attr, token, uattr.is_kernel);
- if (err)
- goto free_prog;
-
/* run eBPF verifier */
err = bpf_check(&prog, attr, uattr, attr_log);
if (err < 0)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e8e21d1a919a..001ac53825da 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -22,6 +22,8 @@
#include <linux/ctype.h>
#include <linux/error-injection.h>
#include <linux/bpf_lsm.h>
+#include <linux/security.h>
+#include <linux/verification.h>
#include <linux/btf_ids.h>
#include <linux/poison.h>
#include <linux/module.h>
@@ -2554,6 +2556,10 @@ fd_array_get_btf_sparse(struct bpf_verifier_env *env, u32 idx)
static struct btf *fd_array_get_btf(struct bpf_verifier_env *env, u32 idx)
{
+ if (env->signature) {
+ verbose(env, "signed program cannot bind any BTF\n");
+ return ERR_PTR(-EACCES);
+ }
if (env->fd_array)
return fd_array_get_btf_continuous(env, idx);
if (!bpfptr_is_null(env->fd_array_raw))
@@ -17627,6 +17633,11 @@ static int __add_used_btf(struct bpf_verifier_env *env, struct btf *btf)
if (env->used_btfs[i].btf == btf)
goto ret_put;
+ if (env->signature) {
+ verbose(env, "signed program cannot bind any BTF\n");
+ ret = -EACCES;
+ goto ret_put;
+ }
if (env->used_btf_cnt >= MAX_USED_BTFS) {
verbose(env, "The total number of btfs per program has reached the limit of %u\n",
MAX_USED_BTFS);
@@ -17909,6 +17920,12 @@ static int __add_used_map(struct bpf_verifier_env *env, struct bpf_map *map)
if (env->used_maps[i] == map)
return i;
+ if (env->signature &&
+ env->prog->aux->sig.verdict == BPF_SIG_VERIFIED) {
+ verbose(env, "signed program cannot bind map '%s' not covered by the signature\n",
+ map->name);
+ return -EACCES;
+ }
if (env->used_map_cnt >= MAX_USED_MAPS) {
verbose(env, "The total number of maps per program has reached the limit of %u\n",
MAX_USED_MAPS);
@@ -17992,6 +18009,10 @@ static int fd_array_get_map_idx(struct bpf_verifier_env *env, u32 idx)
{
if (env->fd_array)
return fd_array_get_map_idx_continuous(env, idx);
+ if (env->signature) {
+ verbose(env, "signed program must bind maps via a continuous fd_array (fd_array_cnt)\n");
+ return -EACCES;
+ }
if (!bpfptr_is_null(env->fd_array_raw))
return fd_array_get_map_idx_sparse(env, idx);
@@ -18270,6 +18291,10 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
map_idx = fd_array_get_map_idx(env, insn[0].imm);
break;
default:
+ if (env->signature) {
+ verbose(env, "signed program cannot reference a map by fd, only via fd_array index\n");
+ return -EINVAL;
+ }
map_idx = add_used_map(env, insn[0].imm);
break;
}
@@ -19851,6 +19876,146 @@ int bpf_fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
return 0;
}
+static enum bpf_sig_keyring bpf_classify_keyring(s32 keyring_id)
+{
+ switch (keyring_id) {
+ case 0:
+ return BPF_SIG_KEYRING_BUILTIN;
+ case (s32)(unsigned long)VERIFY_USE_SECONDARY_KEYRING:
+ return BPF_SIG_KEYRING_SECONDARY;
+ case (s32)(unsigned long)VERIFY_USE_PLATFORM_KEYRING:
+ return BPF_SIG_KEYRING_PLATFORM;
+ default:
+ return BPF_SIG_KEYRING_USER;
+ }
+}
+
+/*
+ * Verify the PKCS#7 signature of a loaded program. Called from bpf_check()
+ * once the program's metadata maps have been resolved into used_maps, so
+ * the exact maps folded into the signature are the ones the program binds.
+ *
+ * The signature covers the instructions followed by the frozen contents of
+ * each map, in @maps order: insns || map_0 || map_1 || [...]. On success the
+ * verdict and keyring info are recorded on prog->aux.
+ */
+static int bpf_prog_verify_signature(struct bpf_verifier_env *env,
+ union bpf_attr *attr, bool is_kernel)
+{
+ bpfptr_t usig = make_bpfptr(attr->signature, is_kernel);
+ struct bpf_dynptr_kern sig_ptr, data_ptr;
+ struct bpf_prog *prog = env->prog;
+ struct bpf_map **maps = env->used_maps;
+ struct bpf_key *key = NULL;
+ void *sig, *data = NULL;
+ u32 map_cnt = env->used_map_cnt;
+ u32 i, off, insns_sz;
+ u64 data_sz;
+ int err = 0;
+
+ /*
+ * Don't attempt to use kmalloc_large or vmalloc for signatures.
+ * Practical signature for BPF program should be below this limit.
+ */
+ if (!attr->signature_size ||
+ attr->signature_size > KMALLOC_MAX_CACHE_SIZE)
+ return -EINVAL;
+ if (system_keyring_id_check(attr->keyring_id) == 0)
+ key = bpf_lookup_system_key(attr->keyring_id);
+ else
+ key = bpf_lookup_user_key(attr->keyring_id, 0);
+ if (!key) {
+ verbose(env, "cannot resolve signing keyring with keyring_id %d\n",
+ attr->keyring_id);
+ return -EINVAL;
+ }
+
+ sig = kvmemdup_bpfptr(usig, attr->signature_size);
+ if (IS_ERR(sig)) {
+ bpf_key_put(key);
+ return PTR_ERR(sig);
+ }
+
+ insns_sz = prog->len * sizeof(struct bpf_insn);
+ data_sz = insns_sz;
+ for (i = 0; i < map_cnt; i++) {
+ struct bpf_map *map = maps[i];
+
+ if (map->map_type != BPF_MAP_TYPE_ARRAY ||
+ !map->ops->map_direct_value_addr) {
+ verbose(env, "signed program metadata map '%s' must be an array\n",
+ map->name);
+ err = -EINVAL;
+ goto out;
+ }
+ if (!READ_ONCE(map->frozen)) {
+ verbose(env, "signed program metadata map '%s' must be frozen\n",
+ map->name);
+ err = -EPERM;
+ goto out;
+ }
+ if (bpf_map_write_active(map)) {
+ verbose(env, "signed program metadata map '%s' has active writers\n",
+ map->name);
+ err = -EBUSY;
+ goto out;
+ }
+ if (!map->excl_prog_sha) {
+ verbose(env, "signed program metadata map '%s' must be exclusive\n",
+ map->name);
+ err = -EPERM;
+ goto out;
+ }
+ data_sz += map->value_size;
+ }
+ if (bpf_dynptr_check_size(data_sz)) {
+ verbose(env, "signed payload too large: %llu bytes\n", data_sz);
+ err = -E2BIG;
+ goto out;
+ }
+ data = kvmalloc(data_sz, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+ if (!data) {
+ err = -ENOMEM;
+ goto out;
+ }
+ memcpy(data, prog->insnsi, insns_sz);
+ off = insns_sz;
+ for (i = 0; i < map_cnt; i++) {
+ struct bpf_map *map = maps[i];
+ u64 addr;
+
+ err = map->ops->map_direct_value_addr(map, &addr, 0);
+ if (err) {
+ verbose(env, "failed to read signed metadata map '%s': %d\n",
+ map->name, err);
+ goto out;
+ }
+ memcpy(data + off, (void *)(unsigned long)addr,
+ map->value_size);
+ off += map->value_size;
+ }
+
+ bpf_dynptr_init(&data_ptr, data, BPF_DYNPTR_TYPE_LOCAL, 0, data_sz);
+ bpf_dynptr_init(&sig_ptr, sig, BPF_DYNPTR_TYPE_LOCAL, 0,
+ attr->signature_size);
+
+ err = bpf_verify_pkcs7_signature((struct bpf_dynptr *)&data_ptr,
+ (struct bpf_dynptr *)&sig_ptr, key);
+ if (err) {
+ verbose(env, "signature verification failed: %d\n", err);
+ } else {
+ verbose(env, "signature verification passed\n");
+ prog->aux->sig.keyring_serial = bpf_key_serial(key);
+ prog->aux->sig.keyring_type = bpf_classify_keyring(attr->keyring_id);
+ prog->aux->sig.verdict = BPF_SIG_VERIFIED;
+ }
+out:
+ kvfree(data);
+ bpf_key_put(key);
+ kvfree(sig);
+ return err;
+}
+
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
struct bpf_log_attr *attr_log)
{
@@ -19873,18 +20038,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
return -ENOMEM;
env->bt.env = env;
-
- len = (*prog)->len;
- env->insn_aux_data =
- vzalloc(array_size(sizeof(struct bpf_insn_aux_data), len));
- ret = -ENOMEM;
- if (!env->insn_aux_data)
- goto err_free_env;
- for (i = 0; i < len; i++)
- env->insn_aux_data[i].orig_idx = i;
- env->succ = bpf_iarray_realloc(NULL, 2);
- if (!env->succ)
- goto err_free_env;
env->prog = *prog;
env->ops = bpf_verifier_ops[env->prog->type];
@@ -19893,22 +20046,51 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
env->bypass_spec_v1 = bpf_bypass_spec_v1(env->prog->aux->token);
env->bypass_spec_v4 = bpf_bypass_spec_v4(env->prog->aux->token);
env->bpf_capable = is_priv = bpf_token_capable(env->prog->aux->token, CAP_BPF);
-
- bpf_get_btf_vmlinux();
-
- /* grab the mutex to protect few globals used by verifier */
- if (!is_priv)
- mutex_lock(&bpf_verifier_lock);
+ env->signature = attr->signature;
/* user could have requested verbose verifier output
* and supplied buffer to store the verification trace
*/
ret = bpf_vlog_init(&env->log, attr_log->level, attr_log->ubuf, attr_log->size);
if (ret)
- goto err_unlock;
+ goto err_free_env;
+ if (env->signature) {
+ ret = bpf_prog_calc_tag(env->prog);
+ if (ret < 0)
+ goto err_prep;
+ }
ret = process_fd_array(env, attr, uattr);
if (ret)
+ goto err_prep;
+
+ if (env->signature) {
+ ret = bpf_prog_verify_signature(env, attr, uattr.is_kernel);
+ if (ret)
+ goto err_prep;
+ }
+
+ ret = security_bpf_prog_load(env->prog, attr, env->prog->aux->token,
+ uattr.is_kernel);
+ if (ret)
+ goto err_prep;
+
+ bpf_get_btf_vmlinux();
+
+ /* grab the mutex to protect few globals used by verifier */
+ if (!is_priv)
+ mutex_lock(&bpf_verifier_lock);
+
+ len = env->prog->len;
+ env->insn_aux_data =
+ vzalloc(array_size(sizeof(struct bpf_insn_aux_data), len));
+ ret = -ENOMEM;
+ if (!env->insn_aux_data)
+ goto skip_full_check;
+ for (i = 0; i < len; i++)
+ env->insn_aux_data[i].orig_idx = i;
+ env->succ = bpf_iarray_realloc(NULL, 2);
+ if (!env->succ)
goto skip_full_check;
mark_verifier_state_clean(env);
@@ -20132,18 +20314,26 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
*prog = env->prog;
module_put(env->attach_btf_mod);
-err_unlock:
if (!is_priv)
mutex_unlock(&bpf_verifier_lock);
- bpf_clear_insn_aux_data(env, 0, env->prog->len);
+ goto err_free_env;
+err_prep:
+ err = bpf_log_attr_finalize(attr_log, &env->log);
+ if (err)
+ ret = err;
+ release_insn_arrays(env);
+ release_maps(env);
+ release_btfs(env);
err_free_env:
+ if (env->insn_aux_data)
+ bpf_clear_insn_aux_data(env, 0, env->prog->len);
+ vfree(env->insn_aux_data);
kvfree(env->fd_array);
bpf_stack_liveness_free(env);
kvfree(env->cfg.insn_postorder);
kvfree(env->scc_info);
kvfree(env->succ);
kvfree(env->gotox_tmp_buf);
- vfree(env->insn_aux_data);
kvfree(env);
return ret;
}
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 4/8] bpftool: Check EVP_Digest when computing excl_prog_hash
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
bpftool_prog_sign() ignores the return value of EVP_Digest(). If the
digest computation fails (context allocation failure, or a digest
fetch failure under OpenSSL), EVP_Digest() returns 0 and leaves the
output buffer untouched, but the function still reports success.
Fixes: 40863f4d6ef2 ("bpftool: Add support for signing BPF programs")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
tools/bpf/bpftool/sign.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/sign.c b/tools/bpf/bpftool/sign.c
index f9b742f4bb10..1257dba8ef2f 100644
--- a/tools/bpf/bpftool/sign.c
+++ b/tools/bpf/bpftool/sign.c
@@ -175,8 +175,11 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
goto cleanup;
}
- EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
- &opts->excl_prog_hash_sz, EVP_sha256(), NULL);
+ if (EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
+ &opts->excl_prog_hash_sz, EVP_sha256(), NULL) != 1) {
+ err = -EIO;
+ goto cleanup;
+ }
bd_out = BIO_new(BIO_s_mem());
if (!bd_out) {
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 5/8] bpftool: Cover loader metadata with the program signature
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
bpftool_prog_sign() signed only the loader instructions. The metadata
blob the loader installs was left to an in-loader hash check, which
the kernel now performs at load time over insns || metadata.
Sign that same concatenation: pass the metadata blob (gen_loader_opts
data) through to bpftool_prog_sign() and feed insns || metadata to
CMS_final(). The excl_prog_hash stays a digest of the instructions
alone; it binds the metadata map to the loader and is matched against
prog->digest by the verifier, independent of what the signature covers.
The signed artifact is now plain data: both bytes the signature
covers are embedded verbatim in the generated skeleton, so signing
and verifying an lskel is an ordinary CMS operation that a signer or
auditor can perform (or reproduce) offline, without analyzing loader
bytecode to establish what the signature actually attests to.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
tools/bpf/bpftool/gen.c | 2 ++
tools/bpf/bpftool/sign.c | 17 +++++++++++++++--
2 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 6ae7262ebe0c..a01d06d22d1a 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -793,6 +793,8 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
if (sign_progs) {
sopts.insns = opts.insns;
sopts.insns_sz = opts.insns_sz;
+ sopts.data = opts.data;
+ sopts.data_sz = opts.data_sz;
sopts.excl_prog_hash = prog_sha;
sopts.excl_prog_hash_sz = sizeof(prog_sha);
sopts.signature = sig_buf;
diff --git a/tools/bpf/bpftool/sign.c b/tools/bpf/bpftool/sign.c
index 1257dba8ef2f..88726a6db6d0 100644
--- a/tools/bpf/bpftool/sign.c
+++ b/tools/bpf/bpftool/sign.c
@@ -135,9 +135,21 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
CMS_ContentInfo *cms = NULL;
long actual_sig_len = 0;
X509 *x509 = NULL;
+ void *data = NULL;
+ size_t data_sz;
int err = 0;
- bd_in = BIO_new_mem_buf(opts->insns, opts->insns_sz);
+ data_sz = (size_t)opts->insns_sz + opts->data_sz;
+ data = malloc(data_sz);
+ if (!data) {
+ err = -ENOMEM;
+ goto cleanup;
+ }
+ memcpy(data, opts->insns, opts->insns_sz);
+ if (opts->data_sz)
+ memcpy((char *)data + opts->insns_sz, opts->data, opts->data_sz);
+
+ bd_in = BIO_new_mem_buf(data, data_sz);
if (!bd_in) {
err = -ENOMEM;
goto cleanup;
@@ -181,7 +193,7 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
goto cleanup;
}
- bd_out = BIO_new(BIO_s_mem());
+ bd_out = BIO_new(BIO_s_mem());
if (!bd_out) {
err = -ENOMEM;
goto cleanup;
@@ -215,6 +227,7 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
X509_free(x509);
EVP_PKEY_free(private_key);
BIO_free(bd_in);
+ free(data);
DISPLAY_OSSL_ERR(err < 0);
return err;
}
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 3/8] libbpf: Drop in-loader metadata check for load-time verification
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
The signed gen_loader used to police its own metadata map from within
BPF: emit_signature_match() read the kernel-cached map->sha[] back
through hardcoded struct bpf_map offsets and compared it against a hash
that compute_sha_update_offsets() baked into the signed instructions,
after a BPF_OBJ_GET_INFO_BY_FD round-trip to populate map->sha[].
The kernel now verifies the metadata at BPF_PROG_LOAD time by folding
the frozen contents of the loader's exclusive fd_array maps into the
signature, so the loader no longer checks anything itself. Generated
loaders thus carry no verification logic of their own anymore: Nothing
in the signing chain depends on emitted loader bytecode doing the right
thing.
On the loading side, skel_internal.h now sets fd_array_cnt for a signed
load so the kernel scans fd_array for the exclusive metadata map -
still frozen, as the kernel requires - and the BPF_OBJ_GET_INFO_BY_FD
round-trip to populate map->sha[] is gone. The struct bpf_map layout
BUILD_BUG_ON()s on the kernel side are removed as well: they only
pinned the ABI for the in-BPF read of map->sha[] that is no longer
needed. Same for the map->excl member. Note: gen_hash is retained; it
still marks a loader as signed so an untrusted host cannot re-dimension
maps or override initial values now covered by the signature.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
include/linux/bpf.h | 1 -
kernel/bpf/syscall.c | 7 ---
tools/lib/bpf/bpf_gen_internal.h | 1 -
tools/lib/bpf/gen_loader.c | 76 +++-----------------------------
tools/lib/bpf/libbpf_internal.h | 1 -
tools/lib/bpf/skel_internal.h | 31 +------------
6 files changed, 9 insertions(+), 108 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index adf53f7edf28..c1a98fa36738 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -299,7 +299,6 @@ struct bpf_map_owner {
struct bpf_map {
u8 sha[SHA256_DIGEST_SIZE];
- u32 excl;
const struct bpf_map_ops *ops;
struct bpf_map *inner_map_meta;
#ifdef CONFIG_SECURITY
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e898fad01aaf..358f2b0ce2bd 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1598,13 +1598,6 @@ static int map_create_alloc(union bpf_attr *attr, bpfptr_t uattr, struct bpf_ver
err = -EFAULT;
goto free_map;
}
-
- /* See libbpf: emit_signature_match() */
- BUILD_BUG_ON(offsetof(struct bpf_map, excl) != SHA256_DIGEST_SIZE);
- BUILD_BUG_ON(!__same_type(map->excl, u32));
- BUILD_BUG_ON(offsetof(struct bpf_map, sha) != 0);
- BUILD_BUG_ON(!__same_type(map->sha, u8[SHA256_DIGEST_SIZE]));
- map->excl = 1;
} else if (attr->excl_prog_hash_size) {
bpf_log(log, "Invalid excl_prog_hash_size.\n");
err = -EINVAL;
diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h
index 49af4260b8e6..042569187752 100644
--- a/tools/lib/bpf/bpf_gen_internal.h
+++ b/tools/lib/bpf/bpf_gen_internal.h
@@ -51,7 +51,6 @@ struct bpf_gen {
__u32 nr_ksyms;
int fd_array;
int nr_fd_array;
- int hash_insn_offset[SHA256_DWORD_SIZE];
};
void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps);
diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
index c7f2d2ac7bb3..6e3dd5242761 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -111,7 +111,6 @@ static void emit2(struct bpf_gen *gen, struct bpf_insn insn1, struct bpf_insn in
static int add_data(struct bpf_gen *gen, const void *data, __u32 size);
static void emit_sys_close_blob(struct bpf_gen *gen, int blob_off);
-static void emit_signature_match(struct bpf_gen *gen);
void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps)
{
@@ -154,8 +153,6 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps
/* R7 contains the error code from sys_bpf. Copy it into R0 and exit. */
emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7));
emit(gen, BPF_EXIT_INSN());
- if (OPTS_GET(gen->opts, gen_hash, false))
- emit_signature_match(gen);
}
static int add_data(struct bpf_gen *gen, const void *data, __u32 size)
@@ -377,8 +374,6 @@ static void emit_sys_close_blob(struct bpf_gen *gen, int blob_off)
__emit_sys_close(gen);
}
-static void compute_sha_update_offsets(struct bpf_gen *gen);
-
int bpf_gen__finish(struct bpf_gen *gen, int nr_progs, int nr_maps)
{
int i;
@@ -408,9 +403,6 @@ int bpf_gen__finish(struct bpf_gen *gen, int nr_progs, int nr_maps)
if (!gen->error) {
struct gen_loader_opts *opts = gen->opts;
- if (OPTS_GET(opts, gen_hash, false))
- compute_sha_update_offsets(gen);
-
opts->insns = gen->insn_start;
opts->insns_sz = gen->insn_cur - gen->insn_start;
opts->data = gen->data_start;
@@ -460,22 +452,6 @@ void bpf_gen__free(struct bpf_gen *gen)
_val; \
})
-static void compute_sha_update_offsets(struct bpf_gen *gen)
-{
- __u64 sha[SHA256_DWORD_SIZE];
- __u64 sha_dw;
- int i;
-
- libbpf_sha256(gen->data_start, gen->data_cur - gen->data_start, (__u8 *)sha);
- for (i = 0; i < SHA256_DWORD_SIZE; i++) {
- struct bpf_insn *insn =
- (struct bpf_insn *)(gen->insn_start + gen->hash_insn_offset[i]);
- sha_dw = tgt_endian(sha[i]);
- insn[0].imm = (__u32)sha_dw;
- insn[1].imm = sha_dw >> 32;
- }
-}
-
void bpf_gen__load_btf(struct bpf_gen *gen, const void *btf_raw_data,
__u32 btf_raw_size)
{
@@ -557,8 +533,9 @@ void bpf_gen__map_create(struct bpf_gen *gen,
* Conditionally update max_entries from the host-supplied loader
* ctx. This sizes the map at runtime, but for a signed loader
* (gen_hash) it would let an untrusted host re-dimension the
- * program's maps after emit_signature_match(), outside what the
- * signature attests to. Keep the signer-provided max_entries
+ * program's maps, outside what the signature attests to: the
+ * metadata blob is covered by the program signature and verified
+ * by the kernel at load time. Keep the signer-provided max_entries
* baked into the blob in that case.
*/
if (map_idx >= 0 && !OPTS_GET(gen->opts, gen_hash, false))
@@ -596,45 +573,6 @@ void bpf_gen__map_create(struct bpf_gen *gen,
emit_sys_close_stack(gen, stack_off(inner_map_fd));
}
-static void emit_signature_match(struct bpf_gen *gen)
-{
- __s64 off;
- int i;
-
- /*
- * Reject if the metadata map is not exclusive. Without exclusivity
- * the cached map->sha[] verified above can be stale: another BPF
- * program with map access could have mutated the contents between
- * BPF_OBJ_GET_INFO_BY_FD and loader execution.
- */
- emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_1, BPF_PSEUDO_MAP_IDX,
- 0, 0, 0, 0));
- emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, SHA256_DIGEST_LENGTH));
- off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 2;
- if (is_simm16(off)) {
- emit(gen, BPF_MOV64_IMM(BPF_REG_7, -EINVAL));
- emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_2, 1, off));
- } else {
- gen->error = -ERANGE;
- }
-
- for (i = 0; i < SHA256_DWORD_SIZE; i++) {
- emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_1, BPF_PSEUDO_MAP_IDX,
- 0, 0, 0, 0));
- emit(gen, BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, i * sizeof(__u64)));
- gen->hash_insn_offset[i] = gen->insn_cur - gen->insn_start;
- emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_3, 0, 0, 0, 0, 0));
-
- off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 2;
- if (is_simm16(off)) {
- emit(gen, BPF_MOV64_IMM(BPF_REG_7, -EINVAL));
- emit(gen, BPF_JMP_REG(BPF_JNE, BPF_REG_2, BPF_REG_3, off));
- } else {
- gen->error = -ERANGE;
- }
- }
-}
-
void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *attach_name,
enum bpf_attach_type type)
{
@@ -1211,10 +1149,10 @@ void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *pvalue,
* }
*
* The runtime initial_value comes from the host-supplied loader
- * ctx and would overwrite the blob value after emit_signature_match()
- * has already validated map->sha[]. For a signed loader (gen_hash)
- * the attested blob value must be authoritative, so skip the override
- * and leave the hashed value in place.
+ * ctx and would overwrite the blob value that the program signature
+ * covers and the kernel verifies at load time. For a signed loader
+ * (gen_hash) the attested blob value must be authoritative, so skip
+ * the override and leave the signed value in place.
*/
if (!OPTS_GET(gen->opts, gen_hash, false)) {
emit(gen, BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_6,
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 04cd303fb5a8..d5b7db703b3f 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -768,7 +768,6 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
int probe_fd(int fd);
#define SHA256_DIGEST_LENGTH 32
-#define SHA256_DWORD_SIZE SHA256_DIGEST_LENGTH / sizeof(__u64)
void libbpf_sha256(const void *data, size_t len, __u8 out[SHA256_DIGEST_LENGTH]);
int probe_sys_bpf_ext(void);
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 74503d358bc8..53fee53d36d5 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -18,10 +18,6 @@
#include "bpf.h"
#endif
-#ifndef SHA256_DIGEST_LENGTH
-#define SHA256_DIGEST_LENGTH 32
-#endif
-
#ifndef __NR_bpf
# if defined(__mips__) && defined(_ABIO32)
# define __NR_bpf 4355
@@ -320,25 +316,6 @@ static inline int skel_link_create(int prog_fd, int target_fd,
return skel_sys_bpf(BPF_LINK_CREATE, &attr, attr_sz);
}
-static inline int skel_obj_get_info_by_fd(int fd)
-{
- const size_t attr_sz = offsetofend(union bpf_attr, info);
- __u8 sha[SHA256_DIGEST_LENGTH];
- struct bpf_map_info info;
- __u32 info_len = sizeof(info);
- union bpf_attr attr;
-
- memset(&info, 0, sizeof(info));
- info.hash = (long) &sha;
- info.hash_size = SHA256_DIGEST_LENGTH;
-
- memset(&attr, 0, attr_sz);
- attr.info.bpf_fd = fd;
- attr.info.info = (long) &info;
- attr.info.info_len = info_len;
- return skel_sys_bpf(BPF_OBJ_GET_INFO_BY_FD, &attr, attr_sz);
-}
-
static inline int skel_map_freeze(int fd)
{
const size_t attr_sz = offsetofend(union bpf_attr, map_fd);
@@ -384,12 +361,6 @@ static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
set_err;
goto out;
}
- err = skel_obj_get_info_by_fd(map_fd);
- if (err < 0) {
- opts->errstr = "failed to fetch obj info";
- set_err;
- goto out;
- }
#endif
memset(&attr, 0, prog_load_attr_sz);
@@ -400,6 +371,8 @@ static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
#ifndef __KERNEL__
attr.signature = (long) opts->signature;
attr.signature_size = opts->signature_sz;
+ if (opts->signature)
+ attr.fd_array_cnt = 1;
#else
if (opts->signature || opts->signature_sz)
pr_warn("signatures are not supported from bpf_preload\n");
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 1/8] bpf: Resolve and cache fd_array objects at load time
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260708075343.358712-1-daniel@iogearbox.net>
The fd_array passed to BPF_PROG_LOAD carries the map and module BTF file
descriptors a program binds. The verifier reads it more than once during
a load: process_fd_array() walks it to bind the maps and BTFs, and
check_and_resolve_insns() and the kfunc BTF resolver later read it again
to resolve the program's BPF_PSEUDO_MAP_IDX* and module kfunc refs.
For signed BPF, we need these upfront in memory, thus resolve each fd to
its object once and cache it by fd_array index, then bind that cached
object for the rest of the load. env->fd_array becomes a small per-slot
{map, btf} cache rather than a bpfptr_t; every later reference is then
an in-bounds lookup of an already-resolved object, and an index outside
the cache is rejected instead of read from user memory:
- continuous (fd_array_cnt given): the caller declares the length and
every entry is resolved and bound up front (used also by the BPF
signed loader)
- sparse (no fd_array_cnt): left as the legacy path with no fd_array
cache; each reference reads its fd from the caller's fd_array and
resolves it on the spot. Deduplication in used_maps and the kfunc BTF
table keeps this correct, and only unsigned programs use this shape.
Split these into separate helpers to make it easier to follow.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Anton Protopopov <a.s.protopopov@gmail.com>
---
include/linux/bpf_verifier.h | 22 +++-
kernel/bpf/verifier.c | 223 +++++++++++++++++++++++++++--------
2 files changed, 193 insertions(+), 52 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 76b8b7627a10..bb57773cde37 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -898,6 +898,14 @@ struct bpf_scc_info {
struct bpf_liveness;
+struct bpf_fd_array {
+ union {
+ struct bpf_map *map;
+ struct btf *btf;
+ unsigned long val;
+ };
+};
+
/* single container for all structs
* one verifier_env per bpf_check() call
*/
@@ -989,7 +997,19 @@ struct bpf_verifier_env {
u32 free_list_size;
u32 explored_states_size;
u32 num_backedges;
- bpfptr_t fd_array;
+ /*
+ * The program's fd_array comes in two shapes, told apart by whether
+ * the caller passed fd_array_cnt. They are mutually exclusive:
+ * - continuous (fd_array_cnt given): ->fd_array holds every entry
+ * resolved to its object up front, indexed by fd_array position,
+ * with ->fd_array_cnt slots; ->fd_array_raw is unused.
+ * - sparse (no fd_array_cnt): ->fd_array is NULL, and entries are
+ * read from ->fd_array_raw (the caller's fd_array) and resolved
+ * on the spot at each reference.
+ */
+ struct bpf_fd_array *fd_array;
+ u32 fd_array_cnt;
+ bpfptr_t fd_array_raw;
/* bit mask to keep track of whether a register has been accessed
* since the last time the function state was printed
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4f42b4e929ad..e8e21d1a919a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2490,6 +2490,79 @@ int bpf_get_kfunc_addr(const struct bpf_prog *prog, u32 func_id,
return 0;
}
+#define BPF_FD_SLOT_BTF 1UL
+
+static void fd_slot_set_map(struct bpf_fd_array *slot, struct bpf_map *map)
+{
+ slot->val = (unsigned long)map;
+}
+
+static void fd_slot_set_btf(struct bpf_fd_array *slot, struct btf *btf)
+{
+ slot->val = (unsigned long)btf | BPF_FD_SLOT_BTF;
+}
+
+static struct bpf_map *fd_slot_map(struct bpf_fd_array slot)
+{
+ if (slot.val & BPF_FD_SLOT_BTF)
+ return NULL;
+ return (struct bpf_map *)slot.val;
+}
+
+static struct btf *fd_slot_btf(struct bpf_fd_array slot)
+{
+ if (!(slot.val & BPF_FD_SLOT_BTF))
+ return NULL;
+ return (struct btf *)(slot.val & ~BPF_FD_SLOT_BTF);
+}
+
+static struct btf *
+fd_array_get_btf_continuous(struct bpf_verifier_env *env, u32 idx)
+{
+ struct btf *btf;
+
+ if (idx >= env->fd_array_cnt) {
+ verbose(env, "kfunc fd_idx %u out of bounds, fd_array_cnt %u\n",
+ idx, env->fd_array_cnt);
+ return ERR_PTR(-EINVAL);
+ }
+ btf = fd_slot_btf(env->fd_array[idx]);
+ if (!btf) {
+ verbose(env, "kfunc fd_idx %u is not a module BTF\n", idx);
+ return ERR_PTR(-EINVAL);
+ }
+ btf_get(btf);
+ return btf;
+}
+
+static struct btf *
+fd_array_get_btf_sparse(struct bpf_verifier_env *env, u32 idx)
+{
+ struct btf *btf;
+ int btf_fd;
+
+ if (copy_from_bpfptr_offset(&btf_fd, env->fd_array_raw,
+ (size_t)idx * sizeof(btf_fd), sizeof(btf_fd)))
+ return ERR_PTR(-EFAULT);
+ btf = btf_get_by_fd(btf_fd);
+ if (IS_ERR(btf)) {
+ verbose(env, "invalid module BTF fd specified\n");
+ return btf;
+ }
+ return btf;
+}
+
+static struct btf *fd_array_get_btf(struct bpf_verifier_env *env, u32 idx)
+{
+ if (env->fd_array)
+ return fd_array_get_btf_continuous(env, idx);
+ if (!bpfptr_is_null(env->fd_array_raw))
+ return fd_array_get_btf_sparse(env, idx);
+
+ verbose(env, "kfunc offset > 0 without fd_array is invalid\n");
+ return ERR_PTR(-EPROTO);
+}
+
static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env,
s16 offset)
{
@@ -2498,7 +2571,6 @@ static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env,
struct bpf_kfunc_btf *b;
struct module *mod;
struct btf *btf;
- int btf_fd;
tab = env->prog->aux->kfunc_btf_tab;
b = bsearch(&kf_btf, tab->descs, tab->nr_descs,
@@ -2509,22 +2581,9 @@ static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env,
return ERR_PTR(-E2BIG);
}
- if (bpfptr_is_null(env->fd_array)) {
- verbose(env, "kfunc offset > 0 without fd_array is invalid\n");
- return ERR_PTR(-EPROTO);
- }
-
- if (copy_from_bpfptr_offset(&btf_fd, env->fd_array,
- offset * sizeof(btf_fd),
- sizeof(btf_fd)))
- return ERR_PTR(-EFAULT);
-
- btf = btf_get_by_fd(btf_fd);
- if (IS_ERR(btf)) {
- verbose(env, "invalid module BTF fd specified\n");
+ btf = fd_array_get_btf(env, offset);
+ if (IS_ERR(btf))
return btf;
- }
-
if (!btf_is_module(btf)) {
verbose(env, "BTF fd for kfunc is not a module BTF\n");
btf_put(btf);
@@ -17902,6 +17961,44 @@ static int add_used_map(struct bpf_verifier_env *env, int fd)
return __add_used_map(env, map);
}
+static int fd_array_get_map_idx_continuous(struct bpf_verifier_env *env, u32 idx)
+{
+ struct bpf_map *map;
+
+ if (idx >= env->fd_array_cnt) {
+ verbose(env, "fd_idx %u out of bounds, fd_array_cnt %u\n",
+ idx, env->fd_array_cnt);
+ return -EINVAL;
+ }
+ map = fd_slot_map(env->fd_array[idx]);
+ if (!map) {
+ verbose(env, "fd_idx %u is not a map\n", idx);
+ return -EINVAL;
+ }
+ return __add_used_map(env, map);
+}
+
+static int fd_array_get_map_idx_sparse(struct bpf_verifier_env *env, u32 idx)
+{
+ int fd;
+
+ if (copy_from_bpfptr_offset(&fd, env->fd_array_raw,
+ (size_t)idx * sizeof(fd), sizeof(fd)))
+ return -EFAULT;
+ return add_used_map(env, fd);
+}
+
+static int fd_array_get_map_idx(struct bpf_verifier_env *env, u32 idx)
+{
+ if (env->fd_array)
+ return fd_array_get_map_idx_continuous(env, idx);
+ if (!bpfptr_is_null(env->fd_array_raw))
+ return fd_array_get_map_idx_sparse(env, idx);
+
+ verbose(env, "fd_idx without fd_array is invalid\n");
+ return -EPROTO;
+}
+
static int check_alu_fields(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
u8 class = BPF_CLASS(insn->code);
@@ -18119,7 +18216,6 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
struct bpf_map *map;
int map_idx;
u64 addr;
- u32 fd;
if (i == insn_cnt - 1 || insn[1].code != 0 ||
insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
@@ -18171,21 +18267,13 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
switch (insn[0].src_reg) {
case BPF_PSEUDO_MAP_IDX_VALUE:
case BPF_PSEUDO_MAP_IDX:
- if (bpfptr_is_null(env->fd_array)) {
- verbose(env, "fd_idx without fd_array is invalid\n");
- return -EPROTO;
- }
- if (copy_from_bpfptr_offset(&fd, env->fd_array,
- insn[0].imm * sizeof(fd),
- sizeof(fd)))
- return -EFAULT;
+ map_idx = fd_array_get_map_idx(env, insn[0].imm);
break;
default:
- fd = insn[0].imm;
+ map_idx = add_used_map(env, insn[0].imm);
break;
}
- map_idx = add_used_map(env, fd);
if (map_idx < 0)
return map_idx;
map = env->used_maps[map_idx];
@@ -19460,7 +19548,7 @@ struct btf *bpf_get_btf_vmlinux(void)
* this case expect that every file descriptor in the array is either a map or
* a BTF. Everything else is considered to be trash.
*/
-static int add_fd_from_fd_array(struct bpf_verifier_env *env, int fd)
+static int add_fd_from_fd_array(struct bpf_verifier_env *env, u32 idx, int fd)
{
struct bpf_map *map;
struct btf *btf;
@@ -19472,51 +19560,83 @@ static int add_fd_from_fd_array(struct bpf_verifier_env *env, int fd)
err = __add_used_map(env, map);
if (err < 0)
return err;
+ fd_slot_set_map(&env->fd_array[idx], map);
return 0;
}
btf = __btf_get_by_fd(f);
if (!IS_ERR(btf)) {
btf_get(btf);
- return __add_used_btf(env, btf);
+ err = __add_used_btf(env, btf);
+ if (err < 0)
+ return err;
+ fd_slot_set_btf(&env->fd_array[idx], btf);
+ return 0;
}
verbose(env, "fd %d is not pointing to valid bpf_map or btf\n", fd);
return PTR_ERR(map);
}
-static int process_fd_array(struct bpf_verifier_env *env, union bpf_attr *attr, bpfptr_t uattr)
+/*
+ * A continuous fd_array is resolved into an in-memory cache with one slot
+ * per entry. The bound here is deliberately generous and not derived from
+ * the per-program object limits: Duplicate entries /are/ permitted, and
+ * the number of distinct maps and BTFs a program can bind is enforced when
+ * each entry is resolved by __add_used_map() and __add_used_btf().
+ */
+#define MAX_FD_ARRAY_CNT 4096
+
+static int process_fd_array_continuous(struct bpf_verifier_env *env,
+ bpfptr_t fd_array, u32 cnt)
{
- size_t size = sizeof(int);
- int ret;
- int fd;
+ int fd, ret;
u32 i;
- env->fd_array = make_bpfptr(attr->fd_array, uattr.is_kernel);
-
- /*
- * The only difference between old (no fd_array_cnt is given) and new
- * APIs is that in the latter case the fd_array is expected to be
- * continuous and is scanned for map fds right away
- */
- if (!attr->fd_array_cnt)
- return 0;
-
- /* Check for integer overflow */
- if (attr->fd_array_cnt >= (U32_MAX / size)) {
- verbose(env, "fd_array_cnt is too big (%u)\n", attr->fd_array_cnt);
- return -EINVAL;
+ if (cnt > MAX_FD_ARRAY_CNT) {
+ verbose(env, "fd_array has too many entries (%u, max %u)\n",
+ cnt, MAX_FD_ARRAY_CNT);
+ return -E2BIG;
}
- for (i = 0; i < attr->fd_array_cnt; i++) {
- if (copy_from_bpfptr_offset(&fd, env->fd_array, i * size, size))
+ env->fd_array = kvcalloc(cnt, sizeof(*env->fd_array),
+ GFP_KERNEL_ACCOUNT);
+ if (!env->fd_array)
+ return -ENOMEM;
+ env->fd_array_cnt = cnt;
+ for (i = 0; i < cnt; i++) {
+ if (copy_from_bpfptr_offset(&fd, fd_array,
+ (size_t)i * sizeof(fd), sizeof(fd)))
return -EFAULT;
-
- ret = add_fd_from_fd_array(env, fd);
+ ret = add_fd_from_fd_array(env, i, fd);
if (ret)
return ret;
}
+ return 0;
+}
+static int process_fd_array(struct bpf_verifier_env *env,
+ union bpf_attr *attr, bpfptr_t uattr)
+{
+ bpfptr_t fd_array = make_bpfptr(attr->fd_array, uattr.is_kernel);
+
+ if (bpfptr_is_null(fd_array)) {
+ if (attr->fd_array_cnt) {
+ verbose(env, "fd_array_cnt %u without fd_array is invalid\n",
+ attr->fd_array_cnt);
+ return -EINVAL;
+ }
+ return 0;
+ }
+ /*
+ * New API: the caller passes fd_array_cnt and a continuous array that
+ * is resolved and bound up front. Legacy API (no fd_array_cnt): keep
+ * the caller's array and resolve entries on the spot at each reference.
+ */
+ if (attr->fd_array_cnt)
+ return process_fd_array_continuous(env, fd_array,
+ attr->fd_array_cnt);
+ env->fd_array_raw = fd_array;
return 0;
}
@@ -20017,6 +20137,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
mutex_unlock(&bpf_verifier_lock);
bpf_clear_insn_aux_data(env, 0, env->prog->len);
err_free_env:
+ kvfree(env->fd_array);
bpf_stack_liveness_free(env);
kvfree(env->cfg.insn_postorder);
kvfree(env->scc_info);
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v6 0/8] Verify BPF signed loader at load time
From: Daniel Borkmann @ 2026-07-08 7:53 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
The BPF signing scheme signs a light skeleton's loader program and lets
the loader vouch for everything else: bpftool bakes the SHA256 of the
metadata map into the loader's instructions, signs the instructions, and
the loader compares the (frozen, exclusive) map against that hash from
within BPF once it runs. The construction is sound as a trusted hash
chain, but the kernel itself never attests the metadata, and that split
has been the recurring objection from the LSM / integrity side since the
scheme was proposed.
This proposal closes both gaps by having the kernel verify the metadata
at BPF_PROG_LOAD time, before the LSM admission hook and before the
verifier, /without/ growing the UAPI. A signed loader binds its metadata
map(s) through the existing fd_array/fd_array_cnt, and exclusive maps
are already bound to the loader's digest via excl_prog_hash. When a
signature is present, the kernel collects the exclusive maps from the
fd_array and appends their frozen contents to the instructions before
PKCS#7 verification, so the signature covers ...
insns || metadata_0 || metadata_1 || [...]
... in fd_array order. The in-loader hash check is dropped from the
gen_loader entirely: generated loaders carry no verification logic
anymore, and signing or verifying a skeleton becomes an ordinary CMS
operation over bytes that sit verbatim in the skeleton, reproducible
offline. A signed program is either BPF_SIG_UNSIGNED or BPF_SIG_VERIFIED
with nothing in between.
There is no new UAPI, we now have a single signature scheme, no LSM
code reaching into BPF internals, no new LSM hook, and unsigned loads
are completely unaffected. It is also less complex since the loader
does not need to deal with BTF, an extra kfunc, etc, as proposed in
an earlier series [0]. Tested against full BPF CI which came back
green. For more details and examples, see the documentation patch in
this series.
[0] https://lore.kernel.org/bpf/20260522023234.3778588-1-kpsingh@kernel.org/
v5 -> v6:
- Added bpf_map_write_active check to close potential race on
arm64 (sashiko)
- Rebased & rest stays as-is
v4 -> v5:
- Squashed patch 2/9 and 3/9 together and dropped Nack (Paul)
- Added Anton's Acked-by on the fd_array cache patch
- Add !attr->signature_size test to reject invalid param
and added BPF selftest for this case
v3 -> v4:
- Fix upper limit in MAX_FD_ARRAY_CNT (Anton)
- Reject !fd_array && attr->fd_array_cnt (Anton)
- Add bpftool patch wrt ignored return value of EVP_Digest() (sashiko)
- Fix setting of gen_loader_fixture_init (sashiko)
- Fix unused map_fd cleanup branch in selftest (bot+bpf-ci)
- Remove now unused map->excl member and adjust selftests
- Added more BPF signed_loader corner case selftest coverage
- Added Paul's Nack wrt bpf_prog_load LSM hook dispute
- Added patch 2 to move bigger allocations below fd_array
resolution (Paul)
v2 -> v3:
- Added first commit to cache and work on objects in fd_array
which was the most recent issue sashiko rightfully complained
- Added more BPF signed_loader selftest coverage to cover that
usage of sparse fd_array or map fds gets rejected
- I left the security_bpf_prog_load as in v2 given preference
from BPF side over adding new hook
v1 -> v2:
- Addressed both sashiko complaints, the TOCTOU bug regarding
fd_array processing, as well as exclusive map checking to
only allow array maps. The validation is now moved into the
verifier before the main verification work happens. This also
gives the opportunity to utilize the verifier log.
Daniel Borkmann (8):
bpf: Resolve and cache fd_array objects at load time
bpf: Verify signed loader metadata at load time
libbpf: Drop in-loader metadata check for load-time verification
bpftool: Check EVP_Digest when computing excl_prog_hash
bpftool: Cover loader metadata with the program signature
selftests/bpf: Adjust bpf_map layout in verifier_map_ptr
selftests/bpf: Verify load-time signed loader metadata
Documentation/bpf: Add BPF signing and enforcement doc
Documentation/bpf/index.rst | 1 +
Documentation/bpf/signing.rst | 497 ++++++++
include/linux/bpf.h | 1 -
include/linux/bpf_verifier.h | 23 +-
kernel/bpf/syscall.c | 83 +-
kernel/bpf/verifier.c | 457 ++++++--
tools/bpf/bpftool/gen.c | 2 +
tools/bpf/bpftool/sign.c | 24 +-
tools/lib/bpf/bpf_gen_internal.h | 1 -
tools/lib/bpf/gen_loader.c | 76 +-
tools/lib/bpf/libbpf_internal.h | 1 -
tools/lib/bpf/skel_internal.h | 31 +-
.../selftests/bpf/prog_tests/signed_loader.c | 1025 ++++++++++++++---
.../selftests/bpf/progs/test_signed_loader.c | 9 +-
.../selftests/bpf/progs/verifier_map_ptr.c | 23 +-
15 files changed, 1815 insertions(+), 439 deletions(-)
create mode 100644 Documentation/bpf/signing.rst
--
2.43.0
^ permalink raw reply
* Re: [PATCH v5 bpf-next 0/3] bpf: add bpf_init_inode_xattr kfunc for atomic inode labeling
From: Kumar Kartikeya Dwivedi @ 2026-07-08 3:12 UTC (permalink / raw)
To: David Windsor, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Eduard Zingerman, Song Liu,
Yonghong Song, John Fastabend, KP Singh, Jiri Olsa,
Kumar Kartikeya Dwivedi, Emil Tsalapatis, Matt Bobrowski,
Paul Moore, James Morris, Serge E . Hallyn, Casey Schaufler,
Stephen Smalley, Ondrej Mosnacek, Mimi Zohar, Roberto Sassu,
Dmitry Kasatkin, Eric Snowberg, Alexander Viro, Christian Brauner,
Jan Kara, Shuah Khan
Cc: bpf, linux-security-module, linux-fsdevel, linux-integrity,
selinux, linux-kselftest, linux-kernel
In-Reply-To: <20260708000956.46138-1-dwindsor@gmail.com>
On Wed Jul 8, 2026 at 2:09 AM CEST, David Windsor wrote:
> Many in-kernel LSMs (SELinux, Smack, IMA) store security labels in
> extended attributes. For these LSMs, atomic labeling during inode
> creation is critical: if the inode becomes accessible before its xattr
> is set, it is briefly unlabeled, which can disrupt LSMs making policy
> decisions based on file labels.
>
> Existing LSMs solve this by setting xattrs directly in the
> inode_init_security hook, which runs before the inode becomes
> accessible. BPF LSM programs currently lack this capability because
> the hook uses an output parameter (xattr_count) that BPF programs
> cannot write to, and existing kfuncs like bpf_set_dentry_xattr
> require a dentry that isn't available until after the inode is
> accessible.
>
> This series introduces the bpf_init_inode_xattr() kfunc, which takes
> the combined inode_init_security xattr context argument and claims a
> slot in it via the new security_lsmxattr_add() LSM helper.
>
There are various CI failures in newly added tests, I don't think any of them
are passing. Please fix before respinning.
https://github.com/kernel-patches/bpf/pull/12730
E.g. both test_init_inode_xattr and test_init_inode_xattr_slot do not have
expected results.
pw-bot: cr
> [...]
^ permalink raw reply
* [PATCH v5 bpf-next 3/3] selftests/bpf: add tests for bpf_init_inode_xattr kfunc
From: David Windsor @ 2026-07-08 0:09 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Jiri Olsa, Kumar Kartikeya Dwivedi,
Emil Tsalapatis, Matt Bobrowski, Paul Moore, James Morris,
Serge E . Hallyn, Casey Schaufler, Stephen Smalley,
Ondrej Mosnacek, Mimi Zohar, Roberto Sassu, Dmitry Kasatkin,
Eric Snowberg, Alexander Viro, Christian Brauner, Jan Kara,
Shuah Khan
Cc: bpf, linux-security-module, linux-fsdevel, linux-integrity,
selinux, linux-kselftest, linux-kernel, David Windsor
In-Reply-To: <20260708000956.46138-1-dwindsor@gmail.com>
Test bpf atomic inode xattr labeling in inode_init_security.
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
tools/testing/selftests/bpf/bpf_kfuncs.h | 5 +
.../selftests/bpf/prog_tests/fs_kfuncs.c | 124 ++++++++++++++++++
.../bpf/progs/test_init_inode_xattr.c | 31 +++++
3 files changed, 160 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
index ae71e9b69051..2639f9f94195 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -92,4 +92,9 @@ extern int bpf_set_dentry_xattr(struct dentry *dentry, const char *name__str,
const struct bpf_dynptr *value_p, int flags) __ksym __weak;
extern int bpf_remove_dentry_xattr(struct dentry *dentry, const char *name__str) __ksym __weak;
+struct lsm_xattrs;
+extern int bpf_init_inode_xattr(struct lsm_xattrs *xattrs,
+ const char *name__str,
+ const struct bpf_dynptr *value_p) __ksym __weak;
+
#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
index 43a26ec69a8e..10be0ab91e70 100644
--- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c
@@ -10,6 +10,7 @@
#include "test_get_xattr.skel.h"
#include "test_set_remove_xattr.skel.h"
#include "test_fsverity.skel.h"
+#include "test_init_inode_xattr.skel.h"
static const char testfile[] = "/tmp/test_progs_fs_kfuncs";
@@ -268,6 +269,123 @@ static void test_fsverity(void)
remove(testfile);
}
+static void test_init_inode_xattr(void)
+{
+ struct test_init_inode_xattr *skel = NULL;
+ int fd = -1, err;
+ char value_out[64];
+ const char *testfile_new = "/tmp/test_progs_fs_kfuncs_new";
+
+ skel = test_init_inode_xattr__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_init_inode_xattr__open_and_load"))
+ return;
+
+ skel->bss->monitored_pid = getpid();
+ err = test_init_inode_xattr__attach(skel);
+ if (!ASSERT_OK(err, "test_init_inode_xattr__attach"))
+ goto out;
+
+ /* Trigger inode_init_security */
+ fd = open(testfile_new, O_CREAT | O_RDWR, 0644);
+ if (!ASSERT_GE(fd, 0, "create_file"))
+ goto out;
+
+ ASSERT_EQ(skel->data->init_result, 0, "init_result");
+
+ /* initxattrs prepends "security." to the name. */
+ err = getxattr(testfile_new, "security.bpf.test_label", value_out,
+ sizeof(value_out));
+ if (err < 0 && errno == ENODATA) {
+ printf("%s:SKIP:filesystem did not apply LSM xattrs\n",
+ __func__);
+ test__skip();
+ goto out;
+ }
+ if (!ASSERT_GE(err, 0, "getxattr"))
+ goto out;
+
+ ASSERT_EQ(err, (int)sizeof(skel->data->xattr_value), "xattr_size");
+ ASSERT_EQ(strncmp(value_out, "unconfined_u:object_r:user_home_t:s0",
+ sizeof("unconfined_u:object_r:user_home_t:s0")), 0,
+ "xattr_value");
+
+out:
+ close(fd);
+ test_init_inode_xattr__destroy(skel);
+ remove(testfile_new);
+}
+
+/* Keep in sync with BPF_LSM_INODE_INIT_XATTRS in include/linux/bpf_lsm.h. */
+#define INIT_INODE_XATTR_MAX 4
+
+/*
+ * Programs may attach to inode_init_security without an attach-time limit, but
+ * the kfunc only lets BPF claim INIT_INODE_XATTR_MAX xattr slots per inode.
+ * Calls beyond that budget are rejected at runtime with -ENOSPC.
+ */
+static void test_init_inode_xattr_slot_limit(void)
+{
+ struct test_init_inode_xattr *skel[INIT_INODE_XATTR_MAX + 1] = {};
+ struct bpf_link *link[INIT_INODE_XATTR_MAX + 1] = {};
+ const char *testfile_slot = "/tmp/test_progs_fs_kfuncs_slot";
+ int ok = 0, nospc = 0, other = 0;
+ int i, fd = -1;
+
+ /* All programs attach successfully; there is no attach-time cap. */
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ skel[i] = test_init_inode_xattr__open();
+ if (!ASSERT_OK_PTR(skel[i], "open"))
+ goto out;
+
+ snprintf(skel[i]->rodata->xattr_name,
+ sizeof(skel[i]->rodata->xattr_name), "bpf.label_%d",
+ i);
+
+ if (!ASSERT_OK(test_init_inode_xattr__load(skel[i]), "load"))
+ goto out;
+
+ skel[i]->bss->monitored_pid = getpid();
+
+ link[i] = bpf_program__attach_lsm(skel[i]->progs.test_init_inode_xattr);
+ if (!ASSERT_OK_PTR(link[i], "attach"))
+ goto out;
+ }
+
+ /* Trigger inode_init_security once with all programs attached. */
+ fd = open(testfile_slot, O_CREAT | O_RDWR, 0644);
+ if (!ASSERT_GE(fd, 0, "create_file"))
+ goto out;
+
+ /*
+ * Exactly INIT_INODE_XATTR_MAX programs claim a slot; the program past
+ * the budget gets -ENOSPC. The order in which programs run is not
+ * guaranteed, so count results instead of indexing.
+ */
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ int res = skel[i]->data->init_result;
+
+ if (res == 0)
+ ok++;
+ else if (res == -ENOSPC)
+ nospc++;
+ else
+ other++;
+ }
+
+ ASSERT_EQ(ok, INIT_INODE_XATTR_MAX, "slots_within_budget");
+ ASSERT_EQ(nospc, 1, "slot_over_budget");
+ ASSERT_EQ(other, 0, "unexpected_result");
+
+out:
+ if (fd >= 0)
+ close(fd);
+ for (i = 0; i <= INIT_INODE_XATTR_MAX; i++) {
+ bpf_link__destroy(link[i]);
+ test_init_inode_xattr__destroy(skel[i]);
+ }
+ remove(testfile_slot);
+}
+
void test_fs_kfuncs(void)
{
/* Matches xattr_names in progs/test_get_xattr.c */
@@ -288,4 +406,10 @@ void test_fs_kfuncs(void)
if (test__start_subtest("fsverity"))
test_fsverity();
+
+ if (test__start_subtest("init_inode_xattr"))
+ test_init_inode_xattr();
+
+ if (test__start_subtest("init_inode_xattr_slot_limit"))
+ test_init_inode_xattr_slot_limit();
}
diff --git a/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c b/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
new file mode 100644
index 000000000000..caade53b87e3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_init_inode_xattr.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Cisco Systems, Inc. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+#include "bpf_kfuncs.h"
+
+char _license[] SEC("license") = "GPL";
+
+__u32 monitored_pid;
+int init_result = -1;
+
+const char xattr_name[16] = "bpf.test_label";
+char xattr_value[] = "unconfined_u:object_r:user_home_t:s0";
+
+SEC("lsm/inode_init_security")
+int BPF_PROG(test_init_inode_xattr, struct inode *inode, struct inode *dir,
+ const struct qstr *qstr, struct lsm_xattrs *xattrs)
+{
+ struct bpf_dynptr value_ptr;
+ __u32 pid;
+
+ pid = bpf_get_current_pid_tgid() >> 32;
+ if (pid != monitored_pid)
+ return 0;
+
+ bpf_dynptr_from_mem(xattr_value, sizeof(xattr_value), 0, &value_ptr);
+ init_result = bpf_init_inode_xattr(xattrs, xattr_name, &value_ptr);
+
+ return 0;
+}
--
2.53.0
^ permalink raw reply related
* [PATCH v5 bpf-next 2/3] bpf: add bpf_init_inode_xattr kfunc for atomic inode labeling
From: David Windsor @ 2026-07-08 0:09 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Jiri Olsa, Kumar Kartikeya Dwivedi,
Emil Tsalapatis, Matt Bobrowski, Paul Moore, James Morris,
Serge E . Hallyn, Casey Schaufler, Stephen Smalley,
Ondrej Mosnacek, Mimi Zohar, Roberto Sassu, Dmitry Kasatkin,
Eric Snowberg, Alexander Viro, Christian Brauner, Jan Kara,
Shuah Khan
Cc: bpf, linux-security-module, linux-fsdevel, linux-integrity,
selinux, linux-kselftest, linux-kernel, David Windsor
In-Reply-To: <20260708000956.46138-1-dwindsor@gmail.com>
Add bpf_init_inode_xattr() kfunc for BPF LSM programs to atomically set
xattrs via the inode_init_security hook using security_lsmxattr_add().
The hook now passes its xattr state as a single struct lsm_xattrs
object, which the kfunc takes directly.
This kfunc is only callable from inode_init_security; the verifier
rejects attempts to call it elsewhere.
A previous attempt [1] required a kmalloc string output protocol for
the xattr name. Since commit 6bcdfd2cac55 ("security: Allow all LSMs to
provide xattrs for inode_init_security hook") [2], the xattr name is no
longer allocated; it is a static constant.
Link: https://kernsec.org/pipermail/linux-security-module-archive/2022-October/034878.html [1]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6bcdfd2cac55 [2]
Suggested-by: Song Liu <song@kernel.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
fs/bpf_fs_kfuncs.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c
index 768aca2dc0f0..ad0025f2264a 100644
--- a/fs/bpf_fs_kfuncs.c
+++ b/fs/bpf_fs_kfuncs.c
@@ -11,7 +11,9 @@
#include <linux/file.h>
#include <linux/kernfs.h>
#include <linux/mm.h>
+#include <linux/security.h>
#include <linux/xattr.h>
+#include <uapi/linux/lsm.h>
__bpf_kfunc_start_defs();
@@ -374,6 +376,39 @@ __bpf_kfunc struct inode *bpf_real_inode(struct dentry *dentry)
return d_real_inode(dentry);
}
+/**
+ * bpf_init_inode_xattr - set an xattr on a new inode from inode_init_security
+ * @xattrs: inode_init_security xattr state from the hook context
+ * @name__str: xattr name (e.g., "bpf.file_label")
+ * @value_p: dynptr containing the xattr value
+ *
+ * Only callable from lsm/inode_init_security programs.
+ *
+ * Return: 0 on success, negative error on failure.
+ */
+__bpf_kfunc int bpf_init_inode_xattr(struct lsm_xattrs *xattrs,
+ const char *name__str,
+ const struct bpf_dynptr *value_p)
+{
+ struct bpf_dynptr_kern *value_ptr = (struct bpf_dynptr_kern *)value_p;
+ const void *value;
+ u32 value_len;
+
+ if (!name__str)
+ return -EINVAL;
+ if (strncmp(name__str, XATTR_BPF_LSM_SUFFIX,
+ sizeof(XATTR_BPF_LSM_SUFFIX) - 1))
+ return -EPERM;
+
+ value_len = __bpf_dynptr_size(value_ptr);
+ value = __bpf_dynptr_data(value_ptr, value_len);
+ if (!value)
+ return -EINVAL;
+
+ return security_lsmxattr_add(xattrs, LSM_ID_BPF, name__str, value,
+ value_len);
+}
+
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(bpf_fs_kfunc_set_ids)
@@ -385,6 +420,7 @@ BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEEPABLE)
BTF_ID_FLAGS(func, bpf_set_dentry_xattr, KF_SLEEPABLE)
BTF_ID_FLAGS(func, bpf_remove_dentry_xattr, KF_SLEEPABLE)
BTF_ID_FLAGS(func, bpf_real_inode, KF_SLEEPABLE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_init_inode_xattr)
BTF_KFUNCS_END(bpf_fs_kfunc_set_ids)
static int bpf_fs_kfuncs_filter(const struct bpf_prog *prog, u32 kfunc_id)
--
2.53.0
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