* Re: [PATCH 2/2] security: Fix call security_backing_file_free second time
From: Paul Moore @ 2026-07-02 21:09 UTC (permalink / raw)
To: Cai Xinchen, jmorris, serge, stephen.smalley.work, omosnace,
amir73il, brauner
Cc: linux-security-module, linux-kernel, selinux, caixinchen1,
lujialin4
In-Reply-To: <20260626011720.1144213-3-caixinchen1@huawei.com>
On Jun 25, 2026 Cai Xinchen <caixinchen1@huawei.com> wrote:
>
> I found the following path:
>
> alloc_empty_backing-file
> init_file(&ff->file, xxx)
> -> file_ref_init(&f->f_ref, 1); // only 1
> error = init_backing_file
> -> security_backing_file_alloc
> -> rc = call_int_hook(backing_file_alloc, ...)
The good news is that as you mentioned, only SELinux defines a
backing_file_alloc hook and it always returns success/0.
> if (unlikely(rc))
> security_backing_file_free(backing_file); // first call
> if (unlikely(error)) {
> fput(&ff->file);
> -> if (unlikely(file_ref_put(&file->f_ref))) // zero
> __fput_deferred(file);
> -> ____fput -> __fput -> file_free(file);
> -> backing_file_free(backing_file(f));
> -> security_backing_file_free(&ff->file); // second call
>
> Currently, only SELinux has the lsm backing_file_alloc hook, and the
> backing_file_free hook is not set. When security_backing_file_free is
> called for the first time, the blobs pointer is set to NULL. Therefore,
> double free will not occur in the code.
>
> Fixes: 6af36aeb147a ("lsm: add backing_file LSM hooks")
> Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>
> ---
> security/security.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/security/security.c b/security/security.c
> index 71aea8fdf014..595d3c73253e 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2468,11 +2468,8 @@ int security_backing_file_alloc(struct file *backing_file,
> rc = lsm_backing_file_alloc(backing_file);
> if (rc)
> return rc;
> - rc = call_int_hook(backing_file_alloc, backing_file, user_file);
> - if (unlikely(rc))
> - security_backing_file_free(backing_file);
>
> - return rc;
> + return call_int_hook(backing_file_alloc, backing_file, user_file);
> }
I think the better option would be to move the
call_void_hook(backing_file_free, ...) call in security_backing_file_free()
into the if-statment true block before we set the backing file's LSM blob
pointer to NULL and free the LSM blob.
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH 1/2] security: Some cleanup code
From: Paul Moore @ 2026-07-02 21:09 UTC (permalink / raw)
To: Cai Xinchen, jmorris, serge, stephen.smalley.work, omosnace,
amir73il, brauner
Cc: linux-security-module, linux-kernel, selinux, caixinchen1,
lujialin4
In-Reply-To: <20260626011720.1144213-2-caixinchen1@huawei.com>
On Jun 25, 2026 Cai Xinchen <caixinchen1@huawei.com> wrote:
>
> Delete an unnecessary blank line and a blobs variable with
> duplicate assignment.
>
> Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>
> ---
> security/lsm_init.c | 1 -
> security/selinux/hooks.c | 1 -
> 2 files changed, 2 deletions(-)
Please split this into two patches: one for the LSM (lsm_init.c) and
one for SELinux (hooks.c). They are two different subsystems, mailing
lists, etc.
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index 7c0fd17f1601..d7384866e3a5 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -290,7 +290,6 @@ static void __init lsm_prepare(struct lsm_info *lsm)
> return;
>
> /* Register the LSM blob sizes. */
> - blobs = lsm->blobs;
> lsm_blob_size_update(&blobs->lbs_cred, &blob_sizes.lbs_cred);
> lsm_blob_size_update(&blobs->lbs_file, &blob_sizes.lbs_file);
> lsm_blob_size_update(&blobs->lbs_backing_file,
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 1a713d96206f..e5930ebc9e37 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1748,7 +1748,6 @@ static int bpf_fd_pass(const struct file *file, u32 sid);
>
> static int __file_has_perm(const struct cred *cred, const struct file *file,
> u32 av, bool bf_user_file)
> -
> {
> struct common_audit_data ad;
> struct inode *inode;
> --
> 2.34.1
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH] lsm: cleanup repeated lsm_blob_size_update() calls in lsm_prepare()
From: Matt Bobrowski @ 2026-07-02 20:18 UTC (permalink / raw)
To: Paul Moore; +Cc: linux-security-module, James Morris, Serge E . Hallyn
In-Reply-To: <dde355196558210f6ca87c1a0745a3a8@paul-moore.com>
On Thu, Jul 02, 2026 at 03:15:02PM -0400, Paul Moore wrote:
> On Jun 29, 2026 Matt Bobrowski <mattbobrowski@google.com> wrote:
> >
> > Centralize the definition of LSM security blob fields using an X-macro
> > (LSM_BLOBS_LIST). This reduces repetitive boilerplate code across
> > struct lsm_blob_sizes, blob size registration in lsm_prepare(), and
> > debug log printing in security_init().
> >
> > Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
> > ---
> > include/linux/lsm_hooks.h | 42 ++++++++++++++++------------
> > security/lsm_init.c | 59 ++++++++++-----------------------------
> > 2 files changed, 38 insertions(+), 63 deletions(-)
> >
> > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> > index b4f8cad53ddb..0e73b22bdeea 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -98,28 +98,34 @@ struct security_hook_list {
> > const struct lsm_id *lsmid;
> > } __randomize_layout;
> >
> > +#define LSM_BLOBS_LIST(X) \
> > + X(cred) \
> > + X(file) \
> > + X(backing_file) \
> > + X(ib) \
> > + X(inode) \
> > + X(sock) \
> > + X(superblock) \
> > + X(ipc) \
> > + X(key) \
> > + X(msg_msg) \
> > + X(perf_event) \
> > + X(task) \
> > + X(tun_dev) \
> > + X(xattr_count) \
> > + X(bdev) \
> > + X(bpf_map) \
> > + X(bpf_prog) \
> > + X(bpf_token)
> > +
> > /*
> > * Security blob size or offset data.
> > + * Note: lbs_xattr_count is the number of xattr slots in new_xattrs array.
> > */
> > struct lsm_blob_sizes {
> > - unsigned int lbs_cred;
> > - unsigned int lbs_file;
> > - unsigned int lbs_backing_file;
> > - unsigned int lbs_ib;
> > - unsigned int lbs_inode;
> > - unsigned int lbs_sock;
> > - unsigned int lbs_superblock;
> > - unsigned int lbs_ipc;
> > - unsigned int lbs_key;
> > - unsigned int lbs_msg_msg;
> > - unsigned int lbs_perf_event;
> > - unsigned int lbs_task;
> > - unsigned int lbs_xattr_count; /* num xattr slots in new_xattrs array */
> > - unsigned int lbs_tun_dev;
> > - unsigned int lbs_bdev;
> > - unsigned int lbs_bpf_map;
> > - unsigned int lbs_bpf_prog;
> > - unsigned int lbs_bpf_token;
> > +#define LSM_BLOB_SIZE(name) unsigned int lbs_##name;
> > + LSM_BLOBS_LIST(LSM_BLOB_SIZE);
> > +#undef LSM_BLOB_SIZE
> > };
>
> Generally speaking I greatly prefer to see the structure fields typed out
> as it makes it easier to find them using grep, code indexers, etc. There
> is a similar argument for the security_init() changes (below).
>
> > diff --git a/security/lsm_init.c b/security/lsm_init.c
> > index 7c0fd17f1601..c256f1c33efa 100644
> > --- a/security/lsm_init.c
> > +++ b/security/lsm_init.c
> > @@ -282,40 +282,24 @@ static void __init lsm_blob_size_update(unsigned int *sz_req,
> > * lsm_prepare - Prepare the LSM framework for a new LSM
> > * @lsm: LSM definition
> > */
> > -static void __init lsm_prepare(struct lsm_info *lsm)
> > +static void __init lsm_prepare(const struct lsm_info *lsm)
> > {
> > struct lsm_blob_sizes *blobs = lsm->blobs;
> >
> > if (!blobs)
> > return;
> >
> > - /* Register the LSM blob sizes. */
> > - blobs = lsm->blobs;
> > - lsm_blob_size_update(&blobs->lbs_cred, &blob_sizes.lbs_cred);
> > - lsm_blob_size_update(&blobs->lbs_file, &blob_sizes.lbs_file);
> > - lsm_blob_size_update(&blobs->lbs_backing_file,
> > - &blob_sizes.lbs_backing_file);
> > - lsm_blob_size_update(&blobs->lbs_ib, &blob_sizes.lbs_ib);
> > - /* inode blob gets an rcu_head in addition to LSM blobs. */
> > + /* The inode blob (inode->i_security) gets an rcu_head in addition to
> > + * LSM blobs.
> > + */
> > if (blobs->lbs_inode && blob_sizes.lbs_inode == 0)
> > blob_sizes.lbs_inode = sizeof(struct rcu_head);
> > - lsm_blob_size_update(&blobs->lbs_inode, &blob_sizes.lbs_inode);
> > - lsm_blob_size_update(&blobs->lbs_ipc, &blob_sizes.lbs_ipc);
> > - lsm_blob_size_update(&blobs->lbs_key, &blob_sizes.lbs_key);
> > - lsm_blob_size_update(&blobs->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> > - lsm_blob_size_update(&blobs->lbs_perf_event,
> > - &blob_sizes.lbs_perf_event);
> > - lsm_blob_size_update(&blobs->lbs_sock, &blob_sizes.lbs_sock);
> > - lsm_blob_size_update(&blobs->lbs_superblock,
> > - &blob_sizes.lbs_superblock);
> > - lsm_blob_size_update(&blobs->lbs_task, &blob_sizes.lbs_task);
> > - lsm_blob_size_update(&blobs->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
> > - lsm_blob_size_update(&blobs->lbs_xattr_count,
> > - &blob_sizes.lbs_xattr_count);
> > - lsm_blob_size_update(&blobs->lbs_bdev, &blob_sizes.lbs_bdev);
> > - lsm_blob_size_update(&blobs->lbs_bpf_map, &blob_sizes.lbs_bpf_map);
> > - lsm_blob_size_update(&blobs->lbs_bpf_prog, &blob_sizes.lbs_bpf_prog);
> > - lsm_blob_size_update(&blobs->lbs_bpf_token, &blob_sizes.lbs_bpf_token);
> > +
> > + /* Register the LSM blob sizes. */
> > +#define UPDATE_LSM_BLOB_SIZE(name) \
> > + lsm_blob_size_update(&blobs->lbs_##name, &blob_sizes.lbs_##name);
> > + LSM_BLOBS_LIST(UPDATE_LSM_BLOB_SIZE);
> > +#undef UPDATE_LSM_BLOB_SIZE
> > }
>
> This is one case where the macro approach *might* have some value, but as
> it is the one instance, and multiple sequential blob operations like this
> are going to be *very* limited, I'm not sure there is enough value to
> be worth the change.
>
> I appreciate the initiative to search out areas that you think could use
> improvement, but for the reasons mentioned, I'm not going to merge this
> patch.
That's not a problem. Perhaps you may want to consider only taking the
minor cleanup targets the redundant lsm->blobs access within
lsm_prepare().
> > @@ -441,25 +425,10 @@ int __init security_init(void)
> > lsm_prepare(*lsm);
> >
> > if (lsm_debug) {
> > - lsm_pr("blob(cred) size %d\n", blob_sizes.lbs_cred);
> > - lsm_pr("blob(file) size %d\n", blob_sizes.lbs_file);
> > - lsm_pr("blob(backing_file) size %d\n",
> > - blob_sizes.lbs_backing_file);
> > - lsm_pr("blob(ib) size %d\n", blob_sizes.lbs_ib);
> > - lsm_pr("blob(inode) size %d\n", blob_sizes.lbs_inode);
> > - lsm_pr("blob(ipc) size %d\n", blob_sizes.lbs_ipc);
> > - lsm_pr("blob(key) size %d\n", blob_sizes.lbs_key);
> > - lsm_pr("blob(msg_msg)_size %d\n", blob_sizes.lbs_msg_msg);
> > - lsm_pr("blob(sock) size %d\n", blob_sizes.lbs_sock);
> > - lsm_pr("blob(superblock) size %d\n", blob_sizes.lbs_superblock);
> > - lsm_pr("blob(perf_event) size %d\n", blob_sizes.lbs_perf_event);
> > - lsm_pr("blob(task) size %d\n", blob_sizes.lbs_task);
> > - lsm_pr("blob(tun_dev) size %d\n", blob_sizes.lbs_tun_dev);
> > - lsm_pr("blob(xattr) count %d\n", blob_sizes.lbs_xattr_count);
> > - lsm_pr("blob(bdev) size %d\n", blob_sizes.lbs_bdev);
> > - lsm_pr("blob(bpf_map) size %d\n", blob_sizes.lbs_bpf_map);
> > - lsm_pr("blob(bpf_prog) size %d\n", blob_sizes.lbs_bpf_prog);
> > - lsm_pr("blob(bpf_token) size %d\n", blob_sizes.lbs_bpf_token);
> > +#define PRINT_LSM_BLOB_SIZE(name) \
> > + lsm_pr("blob(" #name ") size %d\n", blob_sizes.lbs_##name);
> > + LSM_BLOBS_LIST(PRINT_LSM_BLOB_SIZE);
> > +#undef PRINT_LSM_BLOB_SIZE
>
> This is another case where having the text string grep'able can be a good
> thing.
>
> --
> paul-moore.com
^ permalink raw reply
* Re: [PATCH v6 1/4] security: lsm: allow LSMs to register for late_initcall_sync init
From: Yeoreum Yun @ 2026-07-02 19:42 UTC (permalink / raw)
To: Paul Moore
Cc: zohar, linux-security-module, linux-kernel, linux-integrity,
roberto.sassu, noodles, jarkko, sudeep.holla, jmorris, serge,
dmitry.kasatkin, eric.snowberg, jgg
In-Reply-To: <CAHC9VhQXwXHjKcr0SRNQyzKZgCwG1RLPT6kWDLLwEKExfXzzOw@mail.gmail.com>
> On Fri, Jun 5, 2026 at 10:43 AM Yeoreum Yun <yeoreum.yun@arm.com> wrote:
> >
> > There are situations where LSMs have dependencies that might mean they
> > want to be initialised later in the boot process, to ensure those
> > dependencies are available. In particular there are some TPM setups (Arm
> > FF-A devices, SPI attached TPMs) required by IMA which are not
> > guaranteed to be initialised for regular initcall_late.
> >
> > Add an initcall_late_sync option that can be used in these situations.
> >
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > ---
> > include/linux/lsm_hooks.h | 2 ++
> > security/lsm_init.c | 13 +++++++++++--
> > 2 files changed, 13 insertions(+), 2 deletions(-)
>
> Looks good to me, thanks for working on sorting this out.
>
> Acked-by: Paul Moore <paul@paul-moore.com>
Thanks!
>
> --
> paul-moore.com
--
Sincerely,
Yeoreum Yun
^ permalink raw reply
* [PATCH] ipe: fix bracket
From: Manuel Ebner @ 2026-07-02 19:22 UTC (permalink / raw)
To: Fan Wu, Jonathan Corbet, Shuah Khan
Cc: Manuel Ebner, linux-security-module, linux-doc, linux-kernel
Replace nonsensical ')' with '0'.
Signed-off-by: Manuel Ebner <manuelebner@mailbox.org>
---
I'm not 100% sure this patch is good. Please check if this makes sense.
---
Documentation/admin-guide/LSM/ipe.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/LSM/ipe.rst b/Documentation/admin-guide/LSM/ipe.rst
index a756d8158531..bebf14fc2411 100644
--- a/Documentation/admin-guide/LSM/ipe.rst
+++ b/Documentation/admin-guide/LSM/ipe.rst
@@ -502,11 +502,11 @@ The following table lists the error codes that may appear in the errno field whi
Event Examples::
type=1404 audit(1653425689.008:55): enforcing=0 old_enforcing=1 auid=4294967295 ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
- type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=)
+ type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
type=1327 audit(1653425689.008:55): proctitle="-bash"
type=1404 audit(1653425689.008:55): enforcing=1 old_enforcing=0 auid=4294967295 ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
- type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=)
+ type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
type=1327 audit(1653425689.008:55): proctitle="-bash"
This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall.
--
2.54.0
^ permalink raw reply related
* Re: [PATCH] lsm: cleanup repeated lsm_blob_size_update() calls in lsm_prepare()
From: Paul Moore @ 2026-07-02 19:15 UTC (permalink / raw)
To: Matt Bobrowski, linux-security-module
Cc: James Morris, Serge E . Hallyn, Matt Bobrowski
In-Reply-To: <20260629210150.832576-1-mattbobrowski@google.com>
On Jun 29, 2026 Matt Bobrowski <mattbobrowski@google.com> wrote:
>
> Centralize the definition of LSM security blob fields using an X-macro
> (LSM_BLOBS_LIST). This reduces repetitive boilerplate code across
> struct lsm_blob_sizes, blob size registration in lsm_prepare(), and
> debug log printing in security_init().
>
> Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
> ---
> include/linux/lsm_hooks.h | 42 ++++++++++++++++------------
> security/lsm_init.c | 59 ++++++++++-----------------------------
> 2 files changed, 38 insertions(+), 63 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index b4f8cad53ddb..0e73b22bdeea 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -98,28 +98,34 @@ struct security_hook_list {
> const struct lsm_id *lsmid;
> } __randomize_layout;
>
> +#define LSM_BLOBS_LIST(X) \
> + X(cred) \
> + X(file) \
> + X(backing_file) \
> + X(ib) \
> + X(inode) \
> + X(sock) \
> + X(superblock) \
> + X(ipc) \
> + X(key) \
> + X(msg_msg) \
> + X(perf_event) \
> + X(task) \
> + X(tun_dev) \
> + X(xattr_count) \
> + X(bdev) \
> + X(bpf_map) \
> + X(bpf_prog) \
> + X(bpf_token)
> +
> /*
> * Security blob size or offset data.
> + * Note: lbs_xattr_count is the number of xattr slots in new_xattrs array.
> */
> struct lsm_blob_sizes {
> - unsigned int lbs_cred;
> - unsigned int lbs_file;
> - unsigned int lbs_backing_file;
> - unsigned int lbs_ib;
> - unsigned int lbs_inode;
> - unsigned int lbs_sock;
> - unsigned int lbs_superblock;
> - unsigned int lbs_ipc;
> - unsigned int lbs_key;
> - unsigned int lbs_msg_msg;
> - unsigned int lbs_perf_event;
> - unsigned int lbs_task;
> - unsigned int lbs_xattr_count; /* num xattr slots in new_xattrs array */
> - unsigned int lbs_tun_dev;
> - unsigned int lbs_bdev;
> - unsigned int lbs_bpf_map;
> - unsigned int lbs_bpf_prog;
> - unsigned int lbs_bpf_token;
> +#define LSM_BLOB_SIZE(name) unsigned int lbs_##name;
> + LSM_BLOBS_LIST(LSM_BLOB_SIZE);
> +#undef LSM_BLOB_SIZE
> };
Generally speaking I greatly prefer to see the structure fields typed out
as it makes it easier to find them using grep, code indexers, etc. There
is a similar argument for the security_init() changes (below).
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index 7c0fd17f1601..c256f1c33efa 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -282,40 +282,24 @@ static void __init lsm_blob_size_update(unsigned int *sz_req,
> * lsm_prepare - Prepare the LSM framework for a new LSM
> * @lsm: LSM definition
> */
> -static void __init lsm_prepare(struct lsm_info *lsm)
> +static void __init lsm_prepare(const struct lsm_info *lsm)
> {
> struct lsm_blob_sizes *blobs = lsm->blobs;
>
> if (!blobs)
> return;
>
> - /* Register the LSM blob sizes. */
> - blobs = lsm->blobs;
> - lsm_blob_size_update(&blobs->lbs_cred, &blob_sizes.lbs_cred);
> - lsm_blob_size_update(&blobs->lbs_file, &blob_sizes.lbs_file);
> - lsm_blob_size_update(&blobs->lbs_backing_file,
> - &blob_sizes.lbs_backing_file);
> - lsm_blob_size_update(&blobs->lbs_ib, &blob_sizes.lbs_ib);
> - /* inode blob gets an rcu_head in addition to LSM blobs. */
> + /* The inode blob (inode->i_security) gets an rcu_head in addition to
> + * LSM blobs.
> + */
> if (blobs->lbs_inode && blob_sizes.lbs_inode == 0)
> blob_sizes.lbs_inode = sizeof(struct rcu_head);
> - lsm_blob_size_update(&blobs->lbs_inode, &blob_sizes.lbs_inode);
> - lsm_blob_size_update(&blobs->lbs_ipc, &blob_sizes.lbs_ipc);
> - lsm_blob_size_update(&blobs->lbs_key, &blob_sizes.lbs_key);
> - lsm_blob_size_update(&blobs->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> - lsm_blob_size_update(&blobs->lbs_perf_event,
> - &blob_sizes.lbs_perf_event);
> - lsm_blob_size_update(&blobs->lbs_sock, &blob_sizes.lbs_sock);
> - lsm_blob_size_update(&blobs->lbs_superblock,
> - &blob_sizes.lbs_superblock);
> - lsm_blob_size_update(&blobs->lbs_task, &blob_sizes.lbs_task);
> - lsm_blob_size_update(&blobs->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
> - lsm_blob_size_update(&blobs->lbs_xattr_count,
> - &blob_sizes.lbs_xattr_count);
> - lsm_blob_size_update(&blobs->lbs_bdev, &blob_sizes.lbs_bdev);
> - lsm_blob_size_update(&blobs->lbs_bpf_map, &blob_sizes.lbs_bpf_map);
> - lsm_blob_size_update(&blobs->lbs_bpf_prog, &blob_sizes.lbs_bpf_prog);
> - lsm_blob_size_update(&blobs->lbs_bpf_token, &blob_sizes.lbs_bpf_token);
> +
> + /* Register the LSM blob sizes. */
> +#define UPDATE_LSM_BLOB_SIZE(name) \
> + lsm_blob_size_update(&blobs->lbs_##name, &blob_sizes.lbs_##name);
> + LSM_BLOBS_LIST(UPDATE_LSM_BLOB_SIZE);
> +#undef UPDATE_LSM_BLOB_SIZE
> }
This is one case where the macro approach *might* have some value, but as
it is the one instance, and multiple sequential blob operations like this
are going to be *very* limited, I'm not sure there is enough value to
be worth the change.
I appreciate the initiative to search out areas that you think could use
improvement, but for the reasons mentioned, I'm not going to merge this
patch.
> @@ -441,25 +425,10 @@ int __init security_init(void)
> lsm_prepare(*lsm);
>
> if (lsm_debug) {
> - lsm_pr("blob(cred) size %d\n", blob_sizes.lbs_cred);
> - lsm_pr("blob(file) size %d\n", blob_sizes.lbs_file);
> - lsm_pr("blob(backing_file) size %d\n",
> - blob_sizes.lbs_backing_file);
> - lsm_pr("blob(ib) size %d\n", blob_sizes.lbs_ib);
> - lsm_pr("blob(inode) size %d\n", blob_sizes.lbs_inode);
> - lsm_pr("blob(ipc) size %d\n", blob_sizes.lbs_ipc);
> - lsm_pr("blob(key) size %d\n", blob_sizes.lbs_key);
> - lsm_pr("blob(msg_msg)_size %d\n", blob_sizes.lbs_msg_msg);
> - lsm_pr("blob(sock) size %d\n", blob_sizes.lbs_sock);
> - lsm_pr("blob(superblock) size %d\n", blob_sizes.lbs_superblock);
> - lsm_pr("blob(perf_event) size %d\n", blob_sizes.lbs_perf_event);
> - lsm_pr("blob(task) size %d\n", blob_sizes.lbs_task);
> - lsm_pr("blob(tun_dev) size %d\n", blob_sizes.lbs_tun_dev);
> - lsm_pr("blob(xattr) count %d\n", blob_sizes.lbs_xattr_count);
> - lsm_pr("blob(bdev) size %d\n", blob_sizes.lbs_bdev);
> - lsm_pr("blob(bpf_map) size %d\n", blob_sizes.lbs_bpf_map);
> - lsm_pr("blob(bpf_prog) size %d\n", blob_sizes.lbs_bpf_prog);
> - lsm_pr("blob(bpf_token) size %d\n", blob_sizes.lbs_bpf_token);
> +#define PRINT_LSM_BLOB_SIZE(name) \
> + lsm_pr("blob(" #name ") size %d\n", blob_sizes.lbs_##name);
> + LSM_BLOBS_LIST(PRINT_LSM_BLOB_SIZE);
> +#undef PRINT_LSM_BLOB_SIZE
This is another case where having the text string grep'able can be a good
thing.
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH] security: clarify task_prctl hook documentation
From: Paul Moore @ 2026-07-02 18:59 UTC (permalink / raw)
To: Bill Roberts, James Morris, Serge E. Hallyn
Cc: casey, Bill Roberts, linux-security-module, linux-kernel
In-Reply-To: <20260615200325.260057-1-bill.roberts@arm.com>
On Jun 15, 2026 Bill Roberts <bill.roberts@arm.com> wrote:
>
> The task_prctl hook comment incorrectly described the hook as checking
> whether a prctl operation is allowed. In reality, the hook exists for
> LSMs to handle LSM-specific prctl operations.
>
> Update the function description and kernel-doc comment to reflect the
> actual behavior. The old wording appears to have been copied from other
> permission-check hooks despite differing semantics.
>
> Signed-off-by: Bill Roberts <bill.roberts@arm.com>
> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
> Reviewed-by: Serge Hallyn <serge@hallyn.com>
> ---
> security/security.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
Good catch, thanks! Merged into lsm/dev.
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH bpf-next v3 1/6] bpf: Resolve and cache fd_array objects at load time
From: Anton Protopopov @ 2026-07-02 19:06 UTC (permalink / raw)
To: Daniel Borkmann
Cc: ast, kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
bpf, linux-security-module
In-Reply-To: <20260702143605.252797-2-daniel@iogearbox.net>
On 26/07/02 04:36PM, Daniel Borkmann wrote:
> 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 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.
>
> UAPI-wise nothing changes, its just the internals on how BPF processes
> and caches the fd_array favors. Split these into separate helpers for
> continuous versus sparse to make it easier to follow.
Overall looks ok. A few comments below.
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Anton Protopopov <a.s.protopopov@gmail.com>
> ---
> include/linux/bpf_verifier.h | 22 +++-
> kernel/bpf/verifier.c | 209 ++++++++++++++++++++++++++---------
> 2 files changed, 179 insertions(+), 52 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 76b8b7627a10..9f0a4e9a15d7 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
> + * lazily on first 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 25aea4271cd0..44bb6ce17a1c 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);
> @@ -17911,6 +17970,44 @@ 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);
> @@ -18128,7 +18225,6 @@ 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 ||
> @@ -18180,21 +18276,13 @@ 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];
> @@ -19469,7 +19557,7 @@ 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;
> @@ -19481,51 +19569,69 @@ 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)
> +#define MAX_FD_ARRAY_CNT (MAX_USED_MAPS + MAX_KFUNC_BTFS)
> +
> +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) {
So, I _think_ I've done the "unlimited" thing because there can be duplicates
in fd_array. The limit is actually tracked by __add_{map_btf} So here we hard
limit on the size of the fd_array itself. (Even without duplicates, this
fd_array can contain, say, MAX_KFUNC_BTFS different maps, which will be in any
case rejected by __add_used_map.)
> + 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);
> + 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))
> + 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 lazily, on first reference.
> + */
> + if (attr->fd_array_cnt)
> + return process_fd_array_continuous(env, fd_array,
> + attr->fd_array_cnt);
Looks like this returns success in case (!fd_array && attr->fd_array_cnt),
which is a misconfiguration and should be rejected.
> + env->fd_array_raw = fd_array;
> return 0;
> }
>
> @@ -20027,6 +20133,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
> bpf_clear_insn_aux_data(env, 0, env->prog->len);
> vfree(env->insn_aux_data);
> 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
* Re: [PATCH v6 1/4] security: lsm: allow LSMs to register for late_initcall_sync init
From: Paul Moore @ 2026-07-02 18:36 UTC (permalink / raw)
To: Yeoreum Yun, zohar
Cc: linux-security-module, linux-kernel, linux-integrity,
roberto.sassu, noodles, jarkko, sudeep.holla, jmorris, serge,
dmitry.kasatkin, eric.snowberg, jgg
In-Reply-To: <20260605144325.434436-2-yeoreum.yun@arm.com>
On Fri, Jun 5, 2026 at 10:43 AM Yeoreum Yun <yeoreum.yun@arm.com> wrote:
>
> There are situations where LSMs have dependencies that might mean they
> want to be initialised later in the boot process, to ensure those
> dependencies are available. In particular there are some TPM setups (Arm
> FF-A devices, SPI attached TPMs) required by IMA which are not
> guaranteed to be initialised for regular initcall_late.
>
> Add an initcall_late_sync option that can be used in these situations.
>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
> include/linux/lsm_hooks.h | 2 ++
> security/lsm_init.c | 13 +++++++++++--
> 2 files changed, 13 insertions(+), 2 deletions(-)
Looks good to me, thanks for working on sorting this out.
Acked-by: Paul Moore <paul@paul-moore.com>
--
paul-moore.com
^ permalink raw reply
* [PATCH v3] hardening: Default randstruct off with rust for better allmodconfig support
From: Mark Brown @ 2026-07-02 17:37 UTC (permalink / raw)
To: Kees Cook, Gustavo A. R. Silva, Paul Moore, James Morris,
Serge E. Hallyn, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich
Cc: linux-hardening, linux-security-module, linux-kernel,
rust-for-linux, Mark Brown
Currently randstruct does not support rust so we have Kconfig dependencies
which prevent rust being enabled when randstruct is. Unfortunately this
prevents rust being enabled in allmodconfig, our standard coverage build.
randstruct gets turned on by default, then the dependency on !RANDSTRUCT
causes rust to get disabled.
Work around this by disabling randstruct by default if we have a usable
rust toolchain and rust support for the architecture, circular
dependencies prevent us directly depending on !RUST. This means we might
end up with a configuration that disables both rust and randstruct but
hopefully it's more likely go give the expected result.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
Changes in v3:
- Rebase onto v7.2-rc1.
- Link to v2: https://patch.msgid.link/20260605-rust-reverse-randstruct-dep-v2-1-93d38023b6f9@kernel.org
Changes in v2:
- Add a HAVE_RUST in there too.
- Link to v1: https://patch.msgid.link/20260605-rust-reverse-randstruct-dep-v1-1-45ce9ee8d0d1@kernel.org
---
security/Kconfig.hardening | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 6923036e1a2f..81c81ad983ad 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -278,7 +278,7 @@ config CC_HAS_RANDSTRUCT
choice
prompt "Randomize layout of sensitive kernel structures"
- default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
+ default RANDSTRUCT_FULL if !(RUST_IS_AVAILABLE && HAVE_RUST) && COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
default RANDSTRUCT_NONE
help
If you enable this, the layouts of structures that are entirely
---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260605-rust-reverse-randstruct-dep-5a504c861128
Best regards,
--
Mark Brown <broonie@kernel.org>
^ permalink raw reply related
* Re: [PATCH -next] lockdown: Add break in lockdown_write
From: Paul Moore @ 2026-07-02 16:50 UTC (permalink / raw)
To: Xiu Jianfeng, nicolas.bouchinet
Cc: Cai Xinchen, jmorris, serge, linux-security-module, linux-kernel
In-Reply-To: <CAHC9VhRokERQGaB-1Xf0AoAzmT5tys4d+e4pmVY-W-88GQ8Jpg@mail.gmail.com>
On Thu, Jan 22, 2026 at 12:41 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Thu, Jan 22, 2026 at 4:31 AM Xiu Jianfeng <xiujianfeng@huawei.com> wrote:
> > On 1/19/2026 5:12 PM, Cai Xinchen wrote:
> > > After the label is matched successful, any other levels judgements
> > > are meaningless. Therefore, add break to return early
> > >
> > > Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>
> >
> > Looks good to me, thanks.
> >
> > Acked-by: Xiu Jianfeng <xiujianfeng@huawei.com>
> >
> > Paul,
> >
> > Would you mind if this patch went through the LSM tree? :)
>
> Assuming Nicolas is okay with that, I can take this through the LSM tree.
Following up on this as I never saw a response on-list and the patch
doesn't appear to be in Linus' tree.
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH v3 4/5] xfs: replace ns_capable_noaudit
From: Darrick J. Wong @ 2026-07-02 15:58 UTC (permalink / raw)
To: cem
Cc: Jan Kara, Christoph Hellwig, Serge E. Hallyn, Dave Chinner,
Eric Sandeen, linux-xfs, linux-fsdevel, linux-security-module,
linux-kernel
In-Reply-To: <20260702093324.127450-9-cem@kernel.org>
On Thu, Jul 02, 2026 at 11:33:23AM +0200, cem@kernel.org wrote:
> From: Carlos Maiolino <cem@kernel.org>
>
> Now that capable_noaudit() is available, we don't need to keep
> using ns_capable_noaudit() and specifying the usernaspace every single
> time.
>
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Serge E. Hallyn <serge@hallyn.com>
> Cc: Darrick J. Wong <djwong@kernel.org>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: Dr. Thomas Orgis" <thomas.orgis@uni-hamburg.de>
> Cc: linux-xfs@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
> fs/xfs/xfs_fsmap.c | 3 +--
> fs/xfs/xfs_ioctl.c | 2 +-
> fs/xfs/xfs_iops.c | 2 +-
> 3 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> index 7c79fbe0a74c..041bb2105ec6 100644
> --- a/fs/xfs/xfs_fsmap.c
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -1174,8 +1174,7 @@ xfs_getfsmap(
> if (!xfs_getfsmap_check_keys(&head->fmh_keys[0], &head->fmh_keys[1]))
> return -EINVAL;
>
> - use_rmap = xfs_has_rmapbt(mp) &&
> - ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
> + use_rmap = xfs_has_rmapbt(mp) && capable_noaudit(CAP_SYS_ADMIN);
> head->fmh_entries = 0;
>
> /* Set up our device handlers. */
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 1a8af827dde1..374b488f0416 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -647,7 +647,7 @@ xfs_ioctl_setattr_get_trans(
> goto out_error;
>
> error = xfs_trans_alloc_ichange(ip, NULL, NULL, pdqp,
> - ns_capable_noaudit(&init_user_ns, CAP_FOWNER), &tp);
> + capable_noaudit(CAP_FOWNER), &tp);
Not sure why the indentation changed, otherwise the patch looks fine to
me.
--D
> if (error)
> goto out_error;
>
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 205fe2dae732..ce9f8b8468fc 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -835,7 +835,7 @@ xfs_setattr_nonsize(
> }
>
> error = xfs_trans_alloc_ichange(ip, udqp, gdqp, NULL,
> - ns_capable_noaudit(&init_user_ns, CAP_FOWNER),
> + capable_noaudit(CAP_FOWNER),
> &tp);
> if (error)
> goto out_dqrele;
> --
> 2.54.0
>
>
^ permalink raw reply
* Re: [PATCH v3 2/5] capability: Add new capable_noaudit
From: Darrick J. Wong @ 2026-07-02 15:56 UTC (permalink / raw)
To: cem
Cc: Jan Kara, Dave Chinner, Eric Sandeen, linux-xfs, linux-fsdevel,
linux-security-module, linux-kernel, Christoph Hellwig,
Serge Hallyn
In-Reply-To: <20260702093324.127450-5-cem@kernel.org>
On Thu, Jul 02, 2026 at 11:33:19AM +0200, cem@kernel.org wrote:
> From: Carlos Maiolino <cem@kernel.org>
>
> In some situations (quota enforcement bypass in this case) we'd like to
> check for a specific capability without triggering spurious audit
> messages from security modules like selinux.
>
> Add a new helper so we don't need to use ns_capable_noaudit() directly.
>
> V3: remove the extern declaration
>
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Darrick J. Wong <djwong@kernel.org>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: Dr. Thomas Orgis" <thomas.orgis@uni-hamburg.de>
> Cc: linux-xfs@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Serge Hallyn <serge@hallyn.com>
> ---
> include/linux/capability.h | 5 +++++
> kernel/capability.c | 17 +++++++++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index 37db92b3d6f8..f8532d92fcad 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -145,6 +145,7 @@ extern bool has_capability_noaudit(struct task_struct *t, int cap);
> extern bool has_ns_capability_noaudit(struct task_struct *t,
> struct user_namespace *ns, int cap);
> extern bool capable(int cap);
> +bool capable_noaudit(int cap);
> extern bool ns_capable(struct user_namespace *ns, int cap);
> extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
> extern bool ns_capable_setid(struct user_namespace *ns, int cap);
> @@ -167,6 +168,10 @@ static inline bool capable(int cap)
> {
> return true;
> }
> +static inline bool capable_noaudit(int cap)
> +{
> + return true;
> +}
> static inline bool ns_capable(struct user_namespace *ns, int cap)
> {
> return true;
> diff --git a/kernel/capability.c b/kernel/capability.c
> index 829f49ae07b9..2c2d1e8300bd 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -416,6 +416,23 @@ bool capable(int cap)
> return ns_capable(&init_user_ns, cap);
> }
> EXPORT_SYMBOL(capable);
> +
> +/**
> + * capable_noaudit - Determine if the current task has a superior
> + * capability in effect (unaudited).
> + * @cap: The capability to be tested for
> + *
> + * This is the same as capable(), except it uses CAP_OPT_NOAUDIT as to prevent
> + * issuing spurious audit messages.
> + *
> + * This sets PF_SUPERPRIV on the task if the capability is available on the
> + * assumption that it's about to be used.
Same complaint about the documentation as last time:
https://lore.kernel.org/linux-fsdevel/20260626151656.GT6078@frogsfrogsfrogs/
--D
> + */
> +bool capable_noaudit(int cap)
> +{
> + return ns_capable_noaudit(&init_user_ns, cap);
> +}
> +EXPORT_SYMBOL(capable_noaudit);
> #endif /* CONFIG_MULTIUSER */
>
> /**
> --
> 2.54.0
>
>
^ permalink raw reply
* Re: [PATCH bpf-next v3 5/6] selftests/bpf: Verify load-time signed loader metadata
From: Daniel Borkmann @ 2026-07-02 15:28 UTC (permalink / raw)
To: bot+bpf-ci, ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module, andrii, martin.lau,
eddyz87, yonghong.song, clm, ihor.solodrai
In-Reply-To: <038b4c7b60a311cb9905bc88e7f27e6846e9578413afa4b902b0684f44dfd980@mail.kernel.org>
On 7/2/26 5:17 PM, bot+bpf-ci@kernel.org wrote:
[...]
>> +cleanup:
>> + if (btf)
>> + btf__free(btf);
>> + if (map_fd >= 0)
>> + close(map_fd);
>
> This isn't a bug, but was map_fd meant to be dropped from this test?
> It's initialized to -1 and never changed, so the cleanup branch is
> unreachable. The sibling tests signed_map_by_fd_rejected and
> signed_sparse_fd_array_rejected create and close a map_fd, but
> signed_module_kfunc_rejected only uses BTF fds and never assigns
> map_fd.
Ack, will clean up in a v4.
^ permalink raw reply
* Re: [PATCH bpf-next v3 5/6] selftests/bpf: Verify load-time signed loader metadata
From: bot+bpf-ci @ 2026-07-02 15:17 UTC (permalink / raw)
To: daniel, ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module, ast, andrii, daniel,
martin.lau, eddyz87, yonghong.song, clm, ihor.solodrai
In-Reply-To: <20260702143605.252797-6-daniel@iogearbox.net>
[-- Attachment #1: Type: text/plain, Size: 1760 bytes --]
> diff --git a/tools/testing/selftests/bpf/prog_tests/signed_loader.c b/tools/testing/selftests/bpf/prog_tests/signed_loader.c
> index 5fc417e31fc6..b3ac3d9b0e31 100644
> --- a/tools/testing/selftests/bpf/prog_tests/signed_loader.c
> +++ b/tools/testing/selftests/bpf/prog_tests/signed_loader.c
[ ... ]
> @@ -1090,20 +1173,462 @@ static void lsm_signature_verdict(void)
> test_signed_loader_lsm__destroy(lsm);
> }
>
> +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 map_fd = -1, prog_fd, err, fds[2];
> + struct btf *btf = NULL;
[ ... ]
> + 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);
> + if (map_fd >= 0)
> + close(map_fd);
This isn't a bug, but was map_fd meant to be dropped from this test?
It's initialized to -1 and never changed, so the cleanup branch is
unreachable. The sibling tests signed_map_by_fd_rejected and
signed_sparse_fd_array_rejected create and close a map_fd, but
signed_module_kfunc_rejected only uses BTF fds and never assigns
map_fd.
> + run_setup("cleanup", dir);
> +}
[ ... ]
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/28599478014
^ permalink raw reply
* Re: [PATCH v2 1/2] landlock: fix TCP Fast Open connection bypass
From: Mickaël Salaün @ 2026-07-02 14:59 UTC (permalink / raw)
To: Matthieu Buffet
Cc: Bryam Vargas, Günther Noack, linux-security-module,
Mikhail Ivanov, Paul Moore, Eric Dumazet, Neal Cardwell,
linux-kernel, netdev
In-Reply-To: <20260701214628.33319-1-matthieu@buffet.re>
Thanks, applied!
On Wed, Jul 01, 2026 at 11:46:27PM +0200, Matthieu Buffet wrote:
> The documentation of the socket_connect() LSM hook states that it
> controls connecting a socket to a remote address. It has not been the
> case since the addition of TCP Fast Open (RFC 7413) support, which allows
> opening a TCP connection (thus, setting a socket's destination address)
> via the MSG_FASTOPEN flag passed to sendto()/sendmsg()/sendmmsg(). The
> problem then got duplicated into MPTCP.
>
> Landlock did not take it into account when its TCP support was added,
> leaving a bypass of TCP connect policy.
>
> Ideally a call to the LSM hook would be added in the fastopen code path,
> in order to fix this generically. But connect() hooks are designed to run
> with the socket locked, unlike sendmsg() hooks.
>
> Closes: https://github.com/landlock-lsm/linux/issues/41
> Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
> Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
> ---
> security/landlock/net.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/security/landlock/net.c b/security/landlock/net.c
> index cbff59ec3aba..46c17116fcf4 100644
> --- a/security/landlock/net.c
> +++ b/security/landlock/net.c
> @@ -351,6 +351,14 @@ static int hook_socket_sendmsg(struct socket *const sock,
> access_mask_t access_request;
> int ret = 0;
>
> + if ((msg->msg_flags & MSG_FASTOPEN) && address && sk_is_tcp(sock->sk)) {
> + ret = current_check_access_socket(
> + sock, address, addrlen, LANDLOCK_ACCESS_NET_CONNECT_TCP,
> + true);
> + if (ret != 0)
> + return ret;
> + }
> +
> if (sk_is_udp(sock->sk))
> access_request = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP;
> else
> --
> 2.47.3
>
>
^ permalink raw reply
* Re: [RFC PATCH 0/4] Introduce capable_noaudit
From: Carlos Maiolino @ 2026-07-02 14:51 UTC (permalink / raw)
To: Christian Brauner
Cc: linux-fsdevel, jack, djwong, hch, serge, linux-security-module,
linux-kernel, linux-xfs
In-Reply-To: <20260702-fortsetzen-verarbeiten-abfertigung-ead54cb2e597@brauner>
On Thu, Jul 02, 2026 at 03:47:37PM +0200, Christian Brauner wrote:
> On 2026-07-02 10:35 +0200, Carlos Maiolino wrote:
> > On Thu, Jul 02, 2026 at 09:41:39AM +0200, Christian Brauner wrote:
> > > On 2026-06-26 13:45 +0200, cem@kernel.org wrote:
> > > > From: Carlos Maiolino <cem@kernel.org>
> > > >
> > > > In some cases - filesystems quota specifically here - we'd like to check
> > > > for effective capabilities without issuing spurious audit messages and
> > > > without the need to specify a namespace for that.
> > > >
> > > > This series introduce capable_noaudit() which has the same goal as
> > > > capable() but without firing audit messages.
> > > >
> > > > Also, this updates both generic quota and xfs quota code to use that.
> > > >
> > > > The last patch unexports has_capability_noaudit() which was originally
> > > > exported to be used in xfs but turns out it does not meet our needs.
> > > >
> > > > Note this is based on top of a current series I have to remove
> > > > has_capability_noaudit() calls from xfs so the xfs patch won't
> > > > apply cleanly without that series.
> > > >
> > > > If adding this helper is acceptable, I'll turn this into a non-rfc
> > > > series with the required changes to apply properly.
> > > >
> > > > Comments? Flames?
> > >
> > > Convert more, please.
> > >
> >
> > Convert what? :) more callers from capable() to capable_noaudit()?
>
> Yes, there's more code that should use the noaudit variant. Future
> work...
/me writes to his todo list
^ permalink raw reply
* [PATCH bpf-next v3 6/6] Documentation/bpf: Add BPF signing and enforcement doc
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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 | 490 ++++++++++++++++++++++++++++++++++
2 files changed, 491 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..01fa4a1ee014
--- /dev/null
+++ b/Documentation/bpf/signing.rst
@@ -0,0 +1,490 @@
+.. 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 enforced for instance by 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``), 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 program bound
+to a signed loader never has a map the 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 such as
+IPE. 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 attempt. 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". Policy LSMs such as IPE consume the same hooks to
+enforce system policy without writing any BPF.
+
+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,
+certificate and hash are embedded in the generated header; 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 file descriptors bound to the program. ``fd_array_cnt`` must be
+ set for the kernel to scan the array. When a signature is present, every map
+ in the array 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 v3 5/6] selftests/bpf: Verify load-time signed loader metadata
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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
[...]
#410/1 signed_loader/loadtime_no_map:OK
#410/2 signed_loader/loadtime_with_map:OK
#410/3 signed_loader/metadata_match:OK
#410/4 signed_loader/signature_enforced:OK
#410/5 signed_loader/signed_nonexcl_fd_array_rejected:OK
#410/6 signed_loader/signed_nonarray_fd_array_rejected:OK
#410/7 signed_loader/signed_btf_fd_array_rejected:OK
#410/8 signed_loader/signed_module_kfunc_rejected:OK
#410/9 signed_loader/signature_failure_logs:OK
#410/10 signed_loader/signature_too_large:OK
#410/11 signed_loader/signature_bad_keyring:OK
#410/12 signed_loader/metadata_ctx_max_entries_ignored:OK
#410/13 signed_loader/metadata_ctx_initial_value_ignored:OK
#410/14 signed_loader/signature_authenticates_insns:OK
#410/15 signed_loader/hash_requires_frozen:OK
#410/16 signed_loader/no_update_after_freeze:OK
#410/17 signed_loader/freeze_writable_mmap:OK
#410/18 signed_loader/no_writable_mmap_frozen:OK
#410/19 signed_loader/map_hash_matches_libbpf:OK
#410/20 signed_loader/map_hash_multi_element:OK
#410/21 signed_loader/map_hash_bad_size:OK
#410/22 signed_loader/map_hash_unsupported_type:OK
#410/23 signed_loader/lsm_signature_verdict:OK
#410/24 signed_loader/signed_no_fd_array:OK
#410/25 signed_loader/signed_map_by_fd_rejected:OK
#410/26 signed_loader/signed_sparse_fd_array_rejected:OK
#410 signed_loader:OK
Summary: 1/26 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
.../selftests/bpf/prog_tests/signed_loader.c | 859 ++++++++++++++----
1 file changed, 695 insertions(+), 164 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..b3ac3d9b0e31 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 +300,220 @@ 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.)
*/
- 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_LT(fd, 0, "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")) {
+ 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_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;
- bool ran;
- int r;
+ 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.
+ * 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.
*/
- 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_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 void signature_enforced(void)
+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;
+ }
+ if (gen_loader_fixture_init(&f) != 0)
+ goto out;
+ have_fixture = true;
+
+ /*
+ * 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 post-verifier");
+ 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);
}
@@ -495,7 +530,7 @@ 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);
@@ -515,7 +550,7 @@ 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 +610,7 @@ 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 +696,7 @@ 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 +749,7 @@ 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 +796,46 @@ 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);
@@ -1007,10 +1060,11 @@ 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 +1083,7 @@ 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 +1116,51 @@ 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);
@@ -1090,20 +1173,462 @@ 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)
+ return -errno;
+ if (bpf_map_update_elem(map_fd, &key, data, 0) || bpf_map_freeze(map_fd)) {
+ ret = -errno;
+ goto out_map;
+ }
+
+ /* Sign insns || metadata, the same bytes the kernel reconstructs. */
+ buf = malloc((size_t)insns_sz + data_sz);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out_map;
+ }
+ 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_map;
+
+ 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) {
+ *load_ret = -errno;
+ ret = -errno;
+ goto out_map;
+ }
+
+ 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);
+out_map:
+ free(buf);
+ 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 map_fd = -1, 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);
+ if (map_fd >= 0)
+ close(map_fd);
+ 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_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_bad_keyring"))
@@ -1132,4 +1657,10 @@ 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();
}
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v3 4/6] bpftool: Cover loader metadata with the program signature
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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 [0].
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/lkml/ecf0521ed302db672672ebfbc670ecfba36a6e00.camel@HansenPartnership.com [0]
---
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 f9b742f4bb10..7cc991c69dc2 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;
@@ -178,7 +190,7 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
&opts->excl_prog_hash_sz, EVP_sha256(), NULL);
- bd_out = BIO_new(BIO_s_mem());
+ bd_out = BIO_new(BIO_s_mem());
if (!bd_out) {
err = -ENOMEM;
goto cleanup;
@@ -212,6 +224,7 @@ 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 v3 2/6] bpf: Verify signed loader metadata at load time
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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 [0]. 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 [1][2]. 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 [3]. Let's implement the former,
without growing the UAPI.
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. 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.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/CAHC9VhSDkwGgPfrBUh7EgBKEJj_JjnY68c0YAmuuLT_i--GskQ@mail.gmail.com [0]
Link: https://lore.kernel.org/bpf/2f71d6c03698eb17d51f7247efde777627ee578a.camel@HansenPartnership.com [1]
Link: https://lore.kernel.org/lkml/ecf0521ed302db672672ebfbc670ecfba36a6e00.camel@HansenPartnership.com [2]
Link: https://lore.kernel.org/bpf/88703f00d5b7a779728451008626efa45e42db3d.camel@HansenPartnership.com [3]
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/syscall.c | 76 +--------------
kernel/bpf/verifier.c | 175 +++++++++++++++++++++++++++++++++++
3 files changed, 178 insertions(+), 74 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9f0a4e9a15d7..961efb903141 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 44bb6ce17a1c..1609053a0eeb 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))
@@ -17636,6 +17642,11 @@ 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);
@@ -17918,6 +17929,12 @@ 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);
@@ -18001,6 +18018,10 @@ 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);
@@ -18279,6 +18300,10 @@ 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;
}
@@ -19846,6 +19871,139 @@ 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 > 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 (!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 | __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)
{
@@ -19888,6 +20046,7 @@ 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);
+ env->signature = attr->signature;
bpf_get_btf_vmlinux();
@@ -19901,11 +20060,27 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
ret = bpf_vlog_init(&env->log, attr_log->level, attr_log->ubuf, attr_log->size);
if (ret)
goto err_unlock;
+ if (env->signature) {
+ ret = bpf_prog_calc_tag(env->prog);
+ if (ret < 0)
+ goto skip_full_check;
+ }
ret = process_fd_array(env, attr, uattr);
if (ret)
goto skip_full_check;
+ if (env->signature) {
+ ret = bpf_prog_verify_signature(env, attr, uattr.is_kernel);
+ if (ret)
+ goto skip_full_check;
+ }
+
+ ret = security_bpf_prog_load(env->prog, attr, env->prog->aux->token,
+ uattr.is_kernel);
+ if (ret)
+ goto skip_full_check;
+
mark_verifier_state_clean(env);
if (IS_ERR(btf_vmlinux)) {
--
2.43.0
^ permalink raw reply related
* [PATCH bpf-next v3 3/6] libbpf: Drop in-loader metadata check for load-time verification
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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. 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>
---
kernel/bpf/syscall.c | 5 ---
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 | 27 +-----------
5 files changed, 9 insertions(+), 101 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e898fad01aaf..c496c73a8483 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1599,11 +1599,6 @@ static int map_create_alloc(union bpf_attr *attr, bpfptr_t uattr, struct bpf_ver
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");
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..8555ab8af554 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -320,25 +320,6 @@ 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 +365,6 @@ 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 +375,8 @@ 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 v3 1/6] bpf: Resolve and cache fd_array objects at load time
From: Daniel Borkmann @ 2026-07-02 14:36 UTC (permalink / raw)
To: ast
Cc: kpsingh, James.Bottomley, paul, bboscaccy, memxor, torvalds,
a.s.protopopov, bpf, linux-security-module
In-Reply-To: <20260702143605.252797-1-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 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.
UAPI-wise nothing changes, its just the internals on how BPF processes
and caches the fd_array favors. Split these into separate helpers for
continuous versus sparse to make it easier to follow.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Anton Protopopov <a.s.protopopov@gmail.com>
---
include/linux/bpf_verifier.h | 22 +++-
kernel/bpf/verifier.c | 209 ++++++++++++++++++++++++++---------
2 files changed, 179 insertions(+), 52 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 76b8b7627a10..9f0a4e9a15d7 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
+ * lazily on first 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 25aea4271cd0..44bb6ce17a1c 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);
@@ -17911,6 +17970,44 @@ 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);
@@ -18128,7 +18225,6 @@ 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 ||
@@ -18180,21 +18276,13 @@ 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];
@@ -19469,7 +19557,7 @@ 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;
@@ -19481,51 +19569,69 @@ 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)
+#define MAX_FD_ARRAY_CNT (MAX_USED_MAPS + MAX_KFUNC_BTFS)
+
+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);
+ 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))
+ 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 lazily, on first 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;
}
@@ -20027,6 +20133,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
bpf_clear_insn_aux_data(env, 0, env->prog->len);
vfree(env->insn_aux_data);
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 v3 0/6] Verify BPF signed loader at load time
From: Daniel Borkmann @ 2026-07-02 14:35 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/
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 (6):
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: Cover loader metadata with the program signature
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 | 490 ++++++++++
include/linux/bpf_verifier.h | 23 +-
kernel/bpf/syscall.c | 81 +-
kernel/bpf/verifier.c | 384 ++++++--
tools/bpf/bpftool/gen.c | 2 +
tools/bpf/bpftool/sign.c | 17 +-
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 | 27 +-
.../selftests/bpf/prog_tests/signed_loader.c | 859 ++++++++++++++----
12 files changed, 1569 insertions(+), 393 deletions(-)
create mode 100644 Documentation/bpf/signing.rst
--
2.43.0
^ permalink raw reply
* Re: [RFC PATCH 0/4] Introduce capable_noaudit
From: Christian Brauner @ 2026-07-02 13:47 UTC (permalink / raw)
To: Carlos Maiolino
Cc: Christian Brauner, linux-fsdevel, jack, djwong, hch, serge,
linux-security-module, linux-kernel, linux-xfs
In-Reply-To: <akYimPrAcHlv7shR@nidhogg.toxiclabs.cc>
On 2026-07-02 10:35 +0200, Carlos Maiolino wrote:
> On Thu, Jul 02, 2026 at 09:41:39AM +0200, Christian Brauner wrote:
> > On 2026-06-26 13:45 +0200, cem@kernel.org wrote:
> > > From: Carlos Maiolino <cem@kernel.org>
> > >
> > > In some cases - filesystems quota specifically here - we'd like to check
> > > for effective capabilities without issuing spurious audit messages and
> > > without the need to specify a namespace for that.
> > >
> > > This series introduce capable_noaudit() which has the same goal as
> > > capable() but without firing audit messages.
> > >
> > > Also, this updates both generic quota and xfs quota code to use that.
> > >
> > > The last patch unexports has_capability_noaudit() which was originally
> > > exported to be used in xfs but turns out it does not meet our needs.
> > >
> > > Note this is based on top of a current series I have to remove
> > > has_capability_noaudit() calls from xfs so the xfs patch won't
> > > apply cleanly without that series.
> > >
> > > If adding this helper is acceptable, I'll turn this into a non-rfc
> > > series with the required changes to apply properly.
> > >
> > > Comments? Flames?
> >
> > Convert more, please.
> >
>
> Convert what? :) more callers from capable() to capable_noaudit()?
Yes, there's more code that should use the noaudit variant. Future
work...
^ permalink raw reply
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