[PATCH v5 0/7] Landlock: IOCTL support

[PATCH v5 0/7] Landlock: IOCTL support

[Günther Noack]

Hello!

These patches add simple ioctl(2) support to Landlock.

Objective
~~~~~~~~~

Make ioctl(2) requests restrictable with Landlock,
in a way that is useful for real-world applications.

Proposed approach
~~~~~~~~~~~~~~~~~

Introduce the LANDLOCK_ACCESS_FS_IOCTL right, which restricts the use
of ioctl(2) on file descriptors.

We attach IOCTL access rights to opened file descriptors, as we
already do for LANDLOCK_ACCESS_FS_TRUNCATE.

If LANDLOCK_ACCESS_FS_IOCTL is handled (restricted in the ruleset),
the LANDLOCK_ACCESS_FS_IOCTL access right governs the use of all IOCTL
commands.

We make an exception for the common and known-harmless IOCTL commands
FIOCLEX, FIONCLEX, FIONBIO and FIONREAD.  These IOCTL commands are
always permitted.  Their functionality is already available through
fcntl(2).

If additionally(!), the access rights LANDLOCK_ACCESS_FS_READ_FILE,
LANDLOCK_ACCESS_FS_WRITE_FILE or LANDLOCK_ACCESS_FS_READ_DIR are
handled, these access rights also unlock some IOCTL commands which are
considered safe for use with files opened in these ways.

As soon as these access rights are handled, the affected IOCTL
commands can not be permitted through LANDLOCK_ACCESS_FS_IOCTL any
more, but only be permitted through the respective more specific
access rights.  A full list of these access rights is listed below in
this cover letter and in the documentation.

I believe that this approach works for the majority of use cases, and
offers a good trade-off between Landlock API and implementation
complexity and flexibility when the feature is used.

Current limitations
~~~~~~~~~~~~~~~~~~~

With this patch set, ioctl(2) requests can *not* be filtered based on
file type, device number (dev_t) or on the ioctl(2) request number.

On the initial RFC patch set [1], we have reached consensus to start
with this simpler coarse-grained approach, and build additional IOCTL
restriction capabilities on top in subsequent steps.

[1] https://lore.kernel.org/linux-security-module/d4f1395c-d2d4-1860-3a02-2a0c023dd761@digikod.net/

Notable implications of this approach
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* Existing inherited file descriptors stay unaffected
  when a program enables Landlock.

  This means in particular that in common scenarios,
  the terminal's IOCTLs (ioctl_tty(2)) continue to work.

* ioctl(2) continues to be available for file descriptors acquired
  through means other than open(2).  Example: Network sockets,
  memfd_create(2), file descriptors that are already open before the
  Landlock ruleset is enabled.

Examples
~~~~~~~~

Starting a sandboxed shell from $HOME with samples/landlock/sandboxer:

  LL_FS_RO=/ LL_FS_RW=. ./sandboxer /bin/bash

The LANDLOCK_ACCESS_FS_IOCTL right is part of the "read-write" rights
here, so we expect that newly opened files outside of $HOME don't work
with most IOCTL commands.

  * "stty" works: It probes terminal properties

  * "stty </dev/tty" fails: /dev/tty can be reopened, but the IOCTL is
    denied.

  * "eject" fails: ioctls to use CD-ROM drive are denied.

  * "ls /dev" works: It uses ioctl to get the terminal size for
    columnar layout

  * The text editors "vim" and "mg" work.  (GNU Emacs fails because it
    attempts to reopen /dev/tty.)

IOCTL groups
~~~~~~~~~~~~

To decide which IOCTL commands should be blanket-permitted we went
through the list of IOCTL commands mentioned in fs/ioctl.c and looked
at them individually to understand what they are about.  The following
list is for reference.

We should always allow the following IOCTL commands, which are also
available through fcntl(2) with the F_SETFD and F_SETFL commands:

 * FIOCLEX, FIONCLEX - these work on the file descriptor and
   manipulate the close-on-exec flag
 * FIONBIO, FIOASYNC - these work on the struct file and enable
   nonblocking-IO and async flags

The following command is guarded and enabled by either of
LANDLOCK_ACCESS_FS_WRITE_FILE, LANDLOCK_ACCESS_FS_READ_FILE or
LANDLOCK_ACCESS_FS_READ_DIR (G2), once one of them is handled
(otherwise by LANDLOCK_ACCESS_FS_IOCTL):

 * FIOQSIZE - get the size of the opened file

The following commands are guarded and enabled by either of
LANDLOCK_ACCESS_FS_WRITE_FILE or LANDLOCK_ACCESS_FS_READ_FILE (G2),
once one of them is handled (otherwise by LANDLOCK_ACCESS_FS_IOCTL):

These are commands that read file system internals:

 * FS_IOC_FIEMAP - get information about file extent mapping
   (c.f. https://www.kernel.org/doc/Documentation/filesystems/fiemap.txt)
 * FIBMAP - get a file's file system block number
 * FIGETBSZ - get file system blocksize

The following commands are guarded and enabled by
LANDLOCK_ACCESS_FS_READ_FILE (G3), if it is handled (otherwise by
LANDLOCK_ACCESS_FS_IOCTL):

 * FIONREAD - get the number of bytes available for reading (the
   implementation is defined per file type)
 * FIDEDUPRANGE - manipulating shared physical storage between files.

The following commands are guarded and enabled by
LANDLOCK_ACCESS_FS_WRITE_FILE (G4), if it is handled (otherwise by
LANDLOCK_ACCESS_FS_IOCTL):

 * FICLONE, FICLONERANGE - making files share physical storage between
   multiple files.  These only work on some file systems, by design.
 * FS_IOC_RESVSP, FS_IOC_RESVSP64, FS_IOC_UNRESVSP, FS_IOC_UNRESVSP64,
   FS_IOC_ZERO_RANGE: Backwards compatibility with legacy XFS
   preallocation syscalls which predate fallocate(2).

The following commands are also mentioned in fs/ioctl.c, but are not
handled specially and are managed by LANDLOCK_ACCESS_FS_IOCTL together
with all other remaining IOCTL commands:

 * FIFREEZE, FITHAW - work on superblock(!) to freeze/thaw the file
   system. Requires CAP_SYS_ADMIN.
 * Accessing file attributes:
   * FS_IOC_GETFLAGS, FS_IOC_SETFLAGS - manipulate inode flags (ioctl_iflags(2))
   * FS_IOC_FSGETXATTR, FS_IOC_FSSETXATTR - more attributes

Related Work
~~~~~~~~~~~~

OpenBSD's pledge(2) [2] restricts ioctl(2) independent of the file
descriptor which is used.  The implementers maintain multiple
allow-lists of predefined ioctl(2) operations required for different
application domains such as "audio", "bpf", "tty" and "inet".

OpenBSD does not guarantee ABI backwards compatibility to the same
extent as Linux does, so it's easier for them to update these lists in
later versions.  It might not be a feasible approach for Linux though.

[2] https://man.openbsd.org/OpenBSD-7.3/pledge.2

Changes
~~~~~~~

V5:
 * Implementation:
   * move IOCTL group expansion logic into fs.c (implementation suggested by
     mic)
   * rename IOCTL_CMD_G* constants to LANDLOCK_ACCESS_FS_IOCTL_GROUP*
   * fs.c: create ioctl_groups constant
   * add "const" to some variables
 * Formatting and docstring fixes (including wrong kernel-doc format)
 * samples/landlock: fix ABI version and fallback attribute (mic)
 * Documentation
   * move header documentation changes into the implementation commit
   * spell out how FIFREEZE, FITHAW and attribute-manipulation ioctls from
     fs/ioctl.c are handled
   * change ABI 4 to ABI 5 in some missing places
   
V4:
 * use "synthetic" IOCTL access rights, as previously discussed
 * testing changes
   * use a large fixture-based test, for more exhaustive coverage,
     and replace some of the earlier tests with it
 * rebased on mic-next

V3:
 * always permit the IOCTL commands FIOCLEX, FIONCLEX, FIONBIO, FIOASYNC and
   FIONREAD, independent of LANDLOCK_ACCESS_FS_IOCTL
 * increment ABI version in the same commit where the feature is introduced
 * testing changes
   * use FIOQSIZE instead of TTY IOCTL commands
     (FIOQSIZE works with regular files, directories and memfds)
   * run the memfd test with both Landlock enabled and disabled
   * add a test for the always-permitted IOCTL commands

V2:
 * rebased on mic-next
 * added documentation
 * exercise ioctl(2) in the memfd test
 * test: Use layout0 for the test

---

V1: https://lore.kernel.org/linux-security-module/20230502171755.9788-1-gnoack3000@gmail.com/
V2: https://lore.kernel.org/linux-security-module/20230623144329.136541-1-gnoack@google.com/
V3: https://lore.kernel.org/linux-security-module/20230814172816.3907299-1-gnoack@google.com/
V4: https://lore.kernel.org/linux-security-module/20231103155717.78042-1-gnoack@google.com/

Günther Noack (7):
  landlock: Optimize the number of calls to get_access_mask slightly
  landlock: Add IOCTL access right
  selftests/landlock: Test IOCTL support
  selftests/landlock: Test IOCTL with memfds
  selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH)
  samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL
  landlock: Document IOCTL support

 Documentation/userspace-api/landlock.rst     |  74 ++-
 include/uapi/linux/landlock.h                |  58 ++-
 samples/landlock/sandboxer.c                 |  13 +-
 security/landlock/fs.c                       | 150 +++++-
 security/landlock/fs.h                       |  11 +
 security/landlock/limits.h                   |  15 +-
 security/landlock/ruleset.c                  |   5 +-
 security/landlock/ruleset.h                  |   2 +-
 security/landlock/syscalls.c                 |  10 +-
 tools/testing/selftests/landlock/base_test.c |   2 +-
 tools/testing/selftests/landlock/fs_test.c   | 498 ++++++++++++++++++-
 11 files changed, 789 insertions(+), 49 deletions(-)


base-commit: f12f8f84509a084399444c4422661345a15cc713
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 1/7] landlock: Optimize the number of calls to get_access_mask slightly

[Günther Noack]

This call is now going through a function pointer,
and it is not as obvious any more that it will be inlined.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 security/landlock/ruleset.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index ffedc99f2b68..23819457bc3f 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -723,11 +723,12 @@ landlock_init_layer_masks(const struct landlock_ruleset *const domain,
 	/* Saves all handled accesses per layer. */
 	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
 		const unsigned long access_req = access_request;
+		const access_mask_t access_mask =
+			get_access_mask(domain, layer_level);
 		unsigned long access_bit;
 
 		for_each_set_bit(access_bit, &access_req, num_access) {
-			if (BIT_ULL(access_bit) &
-			    get_access_mask(domain, layer_level)) {
+			if (BIT_ULL(access_bit) & access_mask) {
 				(*layer_masks)[access_bit] |=
 					BIT_ULL(layer_level);
 				handled_accesses |= BIT_ULL(access_bit);
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 2/7] landlock: Add IOCTL access right

[Günther Noack]

Introduces the LANDLOCK_ACCESS_FS_IOCTL access right
and increments the Landlock ABI version to 5.

Like the truncate right, these rights are associated with a file
descriptor at the time of open(2), and get respected even when the
file descriptor is used outside of the thread which it was originally
opened in.

A newly enabled Landlock policy therefore does not apply to file
descriptors which are already open.

If the LANDLOCK_ACCESS_FS_IOCTL right is handled, only a small number
of safe IOCTL commands will be permitted on newly opened files.  The
permitted IOCTLs can be configured through the ruleset in limited ways
now.  (See documentation for details.)

Noteworthy scenarios which require special attention:

TTY devices support IOCTLs like TIOCSTI and TIOCLINUX, which can be
used to control shell processes on the same terminal which run at
different privilege levels, which may make it possible to escape a
sandbox.  Because stdin, stdout and stderr are normally inherited
rather than newly opened, IOCTLs are usually permitted on them even
after the Landlock policy is enforced.

Some legitimate file system features, like setting up fscrypt, are
exposed as IOCTL commands on regular files and directories -- users of
Landlock are advised to double check that the sandboxed process does
not need to invoke these IOCTLs.

Known limitations:

The LANDLOCK_ACCESS_FS_IOCTL access right is a coarse-grained control
over IOCTL commands.  Future work will enable a more fine-grained
access control for IOCTLs.

In the meantime, Landlock users may use path-based restrictions in
combination with their knowledge about the file system layout to
control what IOCTLs can be done.  Mounting file systems with the nodev
option can help to distinguish regular files and devices, and give
guarantees about the affected files, which Landlock alone can not give
yet.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 include/uapi/linux/landlock.h                |  58 ++++++-
 security/landlock/fs.c                       | 150 ++++++++++++++++++-
 security/landlock/fs.h                       |  11 ++
 security/landlock/limits.h                   |  15 +-
 security/landlock/ruleset.h                  |   2 +-
 security/landlock/syscalls.c                 |  10 +-
 tools/testing/selftests/landlock/base_test.c |   2 +-
 tools/testing/selftests/landlock/fs_test.c   |   5 +-
 8 files changed, 233 insertions(+), 20 deletions(-)

diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 25c8d7677539..578f268b084b 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -128,7 +128,7 @@ struct landlock_net_port_attr {
  * files and directories.  Files or directories opened before the sandboxing
  * are not subject to these restrictions.
  *
- * A file can only receive these access rights:
+ * The following access rights apply only to files:
  *
  * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
  * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that
@@ -138,12 +138,13 @@ struct landlock_net_port_attr {
  * - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access.
  * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`,
  *   :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with
- *   ``O_TRUNC``. Whether an opened file can be truncated with
- *   :manpage:`ftruncate(2)` is determined during :manpage:`open(2)`, in the
- *   same way as read and write permissions are checked during
- *   :manpage:`open(2)` using %LANDLOCK_ACCESS_FS_READ_FILE and
- *   %LANDLOCK_ACCESS_FS_WRITE_FILE. This access right is available since the
- *   third version of the Landlock ABI.
+ *   ``O_TRUNC``.  This access right is available since the third version of the
+ *   Landlock ABI.
+ *
+ * Whether an opened file can be truncated with :manpage:`ftruncate(2)` or used
+ * with `ioctl(2)` is determined during :manpage:`open(2)`, in the same way as
+ * read and write permissions are checked during :manpage:`open(2)` using
+ * %LANDLOCK_ACCESS_FS_READ_FILE and %LANDLOCK_ACCESS_FS_WRITE_FILE.
  *
  * A directory can receive access rights related to files or directories.  The
  * following access right is applied to the directory itself, and the
@@ -198,13 +199,53 @@ struct landlock_net_port_attr {
  *   If multiple requirements are not met, the ``EACCES`` error code takes
  *   precedence over ``EXDEV``.
  *
+ * The following access right applies both to files and directories:
+ *
+ * - %LANDLOCK_ACCESS_FS_IOCTL: Invoke :manpage:`ioctl(2)` commands on an opened
+ *   file or directory.
+ *
+ *   This access right applies to all :manpage:`ioctl(2)` commands, except of
+ *   ``FIOCLEX``, ``FIONCLEX``, ``FIONBIO`` and ``FIOASYNC``.  These commands
+ *   continue to be invokable independent of the %LANDLOCK_ACCESS_FS_IOCTL
+ *   access right.
+ *
+ *   When certain other access rights are handled in the ruleset, in addition to
+ *   %LANDLOCK_ACCESS_FS_IOCTL, granting these access rights will unlock access
+ *   to additional groups of IOCTL commands, on the affected files:
+ *
+ *   * %LANDLOCK_ACCESS_FS_READ_FILE unlocks access to ``FIOQSIZE``,
+ *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``, ``FIONREAD``,
+ *     ``FIDEDUPRANGE``.
+ *
+ *   * %LANDLOCK_ACCESS_FS_WRITE_FILE unlocks access to ``FIOQSIZE``,
+ *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``, ``FICLONE``,
+ *     ``FICLONERANGE``, ``FS_IOC_RESVSP``, ``FS_IOC_RESVSP64``,
+ *     ``FS_IOC_UNRESVSP``, ``FS_IOC_UNRESVSP64``, ``FS_IOC_ZERO_RANGE``.
+ *
+ *   * %LANDLOCK_ACCESS_FS_READ_DIR unlocks access to ``FIOQSIZE``,
+ *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``.
+ *
+ *   When these access rights are handled in the ruleset, the availability of
+ *   the affected IOCTL commands is not governed by %LANDLOCK_ACCESS_FS_IOCTL
+ *   any more, but by the respective access right.
+ *
+ *   All other IOCTL commands are not handled specially, and are governed by
+ *   %LANDLOCK_ACCESS_FS_IOCTL.  This includes %FS_IOC_GETFLAGS and
+ *   %FS_IOC_SETFLAGS for manipulating inode flags (:manpage:`ioctl_iflags(2)`),
+ *   %FS_IOC_FSFETXATTR and %FS_IOC_FSSETXATTR for manipulating extended
+ *   attributes, as well as %FIFREEZE and %FITHAW for freezing and thawing file
+ *   systems.
+ *
+ *   This access right is available since the fifth version of the Landlock
+ *   ABI.
+ *
  * .. warning::
  *
  *   It is currently not possible to restrict some file-related actions
  *   accessible through these syscall families: :manpage:`chdir(2)`,
  *   :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`chmod(2)`,
  *   :manpage:`chown(2)`, :manpage:`setxattr(2)`, :manpage:`utime(2)`,
- *   :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, :manpage:`access(2)`.
+ *   :manpage:`fcntl(2)`, :manpage:`access(2)`.
  *   Future Landlock evolutions will enable to restrict them.
  */
 /* clang-format off */
@@ -223,6 +264,7 @@ struct landlock_net_port_attr {
 #define LANDLOCK_ACCESS_FS_MAKE_SYM			(1ULL << 12)
 #define LANDLOCK_ACCESS_FS_REFER			(1ULL << 13)
 #define LANDLOCK_ACCESS_FS_TRUNCATE			(1ULL << 14)
+#define LANDLOCK_ACCESS_FS_IOCTL			(1ULL << 15)
 /* clang-format on */
 
 /**
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index bc7c126deea2..4d305ddcbc57 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -7,12 +7,14 @@
  * Copyright © 2021-2022 Microsoft Corporation
  */
 
+#include <asm/ioctls.h>
 #include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/bits.h>
 #include <linux/compiler_types.h>
 #include <linux/dcache.h>
 #include <linux/err.h>
+#include <linux/falloc.h>
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -28,6 +30,7 @@
 #include <linux/types.h>
 #include <linux/wait_bit.h>
 #include <linux/workqueue.h>
+#include <uapi/linux/fiemap.h>
 #include <uapi/linux/landlock.h>
 
 #include "common.h"
@@ -83,6 +86,68 @@ static const struct landlock_object_underops landlock_fs_underops = {
 	.release = release_inode
 };
 
+/* IOCTL helpers */
+
+/**
+ * expand_ioctl() - Return the dst flags from either the src flag or the
+ * %LANDLOCK_ACCESS_FS_IOCTL flag, depending on whether the
+ * %LANDLOCK_ACCESS_FS_IOCTL and src access rights are handled or not.
+ *
+ * @handled: Handled access rights
+ * @access: The access mask to copy values from
+ * @src: A single access right to copy from in @access.
+ * @dst: One or more access rights to copy to
+ *
+ * Returns: @dst, or 0
+ */
+static inline access_mask_t expand_ioctl(const access_mask_t handled,
+					 const access_mask_t access,
+					 const access_mask_t src,
+					 const access_mask_t dst)
+{
+	if (!(handled & LANDLOCK_ACCESS_FS_IOCTL))
+		return 0;
+
+	access_mask_t copy_from = (handled & src) ? src :
+						    LANDLOCK_ACCESS_FS_IOCTL;
+	if (access & copy_from)
+		return dst;
+
+	return 0;
+}
+
+/**
+ * landlock_expand_access_fs() - Returns @access with the synthetic IOCTL group
+ * flags enabled if necessary.
+ *
+ * @handled: Handled FS access rights.
+ * @access: FS access rights to expand.
+ *
+ * Returns: @access expanded by the necessary flags for the synthetic IOCTL
+ * access rights.
+ */
+static inline access_mask_t
+landlock_expand_access_fs(const access_mask_t handled,
+			  const access_mask_t access)
+{
+	return access |
+	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_WRITE_FILE,
+			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
+				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
+				    LANDLOCK_ACCESS_FS_IOCTL_GROUP4) |
+	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_FILE,
+			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
+				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
+				    LANDLOCK_ACCESS_FS_IOCTL_GROUP3) |
+	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_DIR,
+			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1);
+}
+
+access_mask_t landlock_expand_handled_access_fs(const access_mask_t handled)
+{
+	return landlock_expand_access_fs(handled, handled);
+}
+
 /* Ruleset management */
 
 static struct landlock_object *get_inode_object(struct inode *const inode)
@@ -147,7 +212,8 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
 	LANDLOCK_ACCESS_FS_EXECUTE | \
 	LANDLOCK_ACCESS_FS_WRITE_FILE | \
 	LANDLOCK_ACCESS_FS_READ_FILE | \
-	LANDLOCK_ACCESS_FS_TRUNCATE)
+	LANDLOCK_ACCESS_FS_TRUNCATE | \
+	LANDLOCK_ACCESS_FS_IOCTL)
 /* clang-format on */
 
 /*
@@ -157,6 +223,7 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 			    const struct path *const path,
 			    access_mask_t access_rights)
 {
+	access_mask_t handled;
 	int err;
 	struct landlock_id id = {
 		.type = LANDLOCK_KEY_INODE,
@@ -169,9 +236,11 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 	if (WARN_ON_ONCE(ruleset->num_layers != 1))
 		return -EINVAL;
 
+	handled = landlock_get_fs_access_mask(ruleset, 0);
+	/* Expands the synthetic IOCTL groups. */
+	access_rights |= landlock_expand_access_fs(handled, access_rights);
 	/* Transforms relative access rights to absolute ones. */
-	access_rights |= LANDLOCK_MASK_ACCESS_FS &
-			 ~landlock_get_fs_access_mask(ruleset, 0);
+	access_rights |= LANDLOCK_MASK_ACCESS_FS & ~handled;
 	id.key.object = get_inode_object(d_backing_inode(path->dentry));
 	if (IS_ERR(id.key.object))
 		return PTR_ERR(id.key.object);
@@ -1119,11 +1188,17 @@ static int hook_file_alloc_security(struct file *const file)
 	return 0;
 }
 
+static const access_mask_t ioctl_groups =
+	LANDLOCK_ACCESS_FS_IOCTL_GROUP1 | LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
+	LANDLOCK_ACCESS_FS_IOCTL_GROUP3 | LANDLOCK_ACCESS_FS_IOCTL_GROUP4;
+
 static int hook_file_open(struct file *const file)
 {
 	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
 	access_mask_t open_access_request, full_access_request, allowed_access;
-	const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
+	const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE |
+					      LANDLOCK_ACCESS_FS_IOCTL |
+					      ioctl_groups;
 	const struct landlock_ruleset *const dom = get_current_fs_domain();
 
 	if (!dom)
@@ -1196,6 +1271,72 @@ static int hook_file_truncate(struct file *const file)
 	return -EACCES;
 }
 
+/**
+ * required_ioctl_access(): Determine required IOCTL access rights.
+ *
+ * @cmd: The IOCTL command that is supposed to be run.
+ *
+ * Returns: The access rights that must be granted on an opened file in order to
+ * use the given @cmd.
+ */
+static access_mask_t required_ioctl_access(unsigned int cmd)
+{
+	switch (cmd) {
+	case FIOCLEX:
+	case FIONCLEX:
+	case FIONBIO:
+	case FIOASYNC:
+		/*
+		 * FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC manipulate the FD's
+		 * close-on-exec and the file's buffered-IO and async flags.
+		 * These operations are also available through fcntl(2),
+		 * and are unconditionally permitted in Landlock.
+		 */
+		return 0;
+	case FIOQSIZE:
+		return LANDLOCK_ACCESS_FS_IOCTL_GROUP1;
+	case FS_IOC_FIEMAP:
+	case FIBMAP:
+	case FIGETBSZ:
+		return LANDLOCK_ACCESS_FS_IOCTL_GROUP2;
+	case FIONREAD:
+	case FIDEDUPERANGE:
+		return LANDLOCK_ACCESS_FS_IOCTL_GROUP3;
+	case FICLONE:
+	case FICLONERANGE:
+	case FS_IOC_RESVSP:
+	case FS_IOC_RESVSP64:
+	case FS_IOC_UNRESVSP:
+	case FS_IOC_UNRESVSP64:
+	case FS_IOC_ZERO_RANGE:
+		return LANDLOCK_ACCESS_FS_IOCTL_GROUP4;
+	default:
+		/*
+		 * Other commands are guarded by the catch-all access right.
+		 */
+		return LANDLOCK_ACCESS_FS_IOCTL;
+	}
+}
+
+static int hook_file_ioctl(struct file *file, unsigned int cmd,
+			   unsigned long arg)
+{
+	const access_mask_t required_access = required_ioctl_access(cmd);
+	const access_mask_t allowed_access =
+		landlock_file(file)->allowed_access;
+
+	/*
+	 * It is the access rights at the time of opening the file which
+	 * determine whether ioctl can be used on the opened file later.
+	 *
+	 * The access right is attached to the opened file in hook_file_open().
+	 */
+	if ((allowed_access & required_access) == required_access)
+		return 0;
+
+	return -EACCES;
+}
+
 static struct security_hook_list landlock_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
 
@@ -1218,6 +1359,7 @@ static struct security_hook_list landlock_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(file_alloc_security, hook_file_alloc_security),
 	LSM_HOOK_INIT(file_open, hook_file_open),
 	LSM_HOOK_INIT(file_truncate, hook_file_truncate),
+	LSM_HOOK_INIT(file_ioctl, hook_file_ioctl),
 };
 
 __init void landlock_add_fs_hooks(void)
diff --git a/security/landlock/fs.h b/security/landlock/fs.h
index 488e4813680a..b3ef11968160 100644
--- a/security/landlock/fs.h
+++ b/security/landlock/fs.h
@@ -92,4 +92,15 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
 			    const struct path *const path,
 			    access_mask_t access_hierarchy);
 
+/**
+ * landlock_expand_handled_access_fs() - add synthetic IOCTL access rights to an
+ * access mask of handled accesses.
+ *
+ * @handled: The handled accesses of a ruleset that is being created
+ *
+ * Returns: @handled, with the bits for the synthetic IOCTL access rights set,
+ * if %LANDLOCK_ACCESS_FS_IOCTL is handled
+ */
+access_mask_t landlock_expand_handled_access_fs(const access_mask_t handled);
+
 #endif /* _SECURITY_LANDLOCK_FS_H */
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 93c9c6f91556..75e822f878e0 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -18,7 +18,20 @@
 #define LANDLOCK_MAX_NUM_LAYERS		16
 #define LANDLOCK_MAX_NUM_RULES		U32_MAX
 
-#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_TRUNCATE
+#define LANDLOCK_LAST_PUBLIC_ACCESS_FS	LANDLOCK_ACCESS_FS_IOCTL
+#define LANDLOCK_MASK_PUBLIC_ACCESS_FS	((LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1) - 1)
+
+/*
+ * These are synthetic access rights, which are only used within the kernel, but
+ * not exposed to callers in userspace.  The mapping between these access rights
+ * and IOCTL commands is defined in the required_ioctl_access() helper function.
+ */
+#define LANDLOCK_ACCESS_FS_IOCTL_GROUP1	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1)
+#define LANDLOCK_ACCESS_FS_IOCTL_GROUP2	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 2)
+#define LANDLOCK_ACCESS_FS_IOCTL_GROUP3	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 3)
+#define LANDLOCK_ACCESS_FS_IOCTL_GROUP4	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 4)
+
+#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_IOCTL_GROUP4
 #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
 #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
 #define LANDLOCK_SHIFT_ACCESS_FS	0
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index c7f1526784fd..5a28ea8e1c3d 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -30,7 +30,7 @@
 	LANDLOCK_ACCESS_FS_REFER)
 /* clang-format on */
 
-typedef u16 access_mask_t;
+typedef u32 access_mask_t;
 /* Makes sure all filesystem access rights can be stored. */
 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
 /* Makes sure all network access rights can be stored. */
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 898358f57fa0..c196cac2a5fb 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -137,7 +137,7 @@ static const struct file_operations ruleset_fops = {
 	.write = fop_dummy_write,
 };
 
-#define LANDLOCK_ABI_VERSION 4
+#define LANDLOCK_ABI_VERSION 5
 
 /**
  * sys_landlock_create_ruleset - Create a new ruleset
@@ -192,8 +192,8 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 		return err;
 
 	/* Checks content (and 32-bits cast). */
-	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
-	    LANDLOCK_MASK_ACCESS_FS)
+	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_PUBLIC_ACCESS_FS) !=
+	    LANDLOCK_MASK_PUBLIC_ACCESS_FS)
 		return -EINVAL;
 
 	/* Checks network content (and 32-bits cast). */
@@ -201,6 +201,10 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 	    LANDLOCK_MASK_ACCESS_NET)
 		return -EINVAL;
 
+	/* Expands synthetic IOCTL groups. */
+	ruleset_attr.handled_access_fs = landlock_expand_handled_access_fs(
+		ruleset_attr.handled_access_fs);
+
 	/* Checks arguments and transforms to kernel struct. */
 	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
 					  ruleset_attr.handled_access_net);
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 646f778dfb1e..d292b419ccba 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -75,7 +75,7 @@ TEST(abi_version)
 	const struct landlock_ruleset_attr ruleset_attr = {
 		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
 	};
-	ASSERT_EQ(4, landlock_create_ruleset(NULL, 0,
+	ASSERT_EQ(5, landlock_create_ruleset(NULL, 0,
 					     LANDLOCK_CREATE_RULESET_VERSION));
 
 	ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 18e1f86a6234..256cd9a96eb7 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -525,9 +525,10 @@ TEST_F_FORK(layout1, inval)
 	LANDLOCK_ACCESS_FS_EXECUTE | \
 	LANDLOCK_ACCESS_FS_WRITE_FILE | \
 	LANDLOCK_ACCESS_FS_READ_FILE | \
-	LANDLOCK_ACCESS_FS_TRUNCATE)
+	LANDLOCK_ACCESS_FS_TRUNCATE | \
+	LANDLOCK_ACCESS_FS_IOCTL)
 
-#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE
+#define ACCESS_LAST LANDLOCK_ACCESS_FS_IOCTL
 
 #define ACCESS_ALL ( \
 	ACCESS_FILE | \
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 3/7] selftests/landlock: Test IOCTL support

[Günther Noack]

Exercises Landlock's IOCTL feature in different combinations of
handling and permitting the rights LANDLOCK_ACCESS_FS_IOCTL,
LANDLOCK_ACCESS_FS_READ_FILE, LANDLOCK_ACCESS_FS_WRITE_FILE and
LANDLOCK_ACCESS_FS_READ_DIR, and in different combinations of using
files and directories.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 tools/testing/selftests/landlock/fs_test.c | 423 ++++++++++++++++++++-
 1 file changed, 420 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 256cd9a96eb7..564e73087e08 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -9,6 +9,7 @@
 
 #define _GNU_SOURCE
 #include <fcntl.h>
+#include <linux/fs.h>
 #include <linux/landlock.h>
 #include <linux/magic.h>
 #include <sched.h>
@@ -3380,7 +3381,7 @@ TEST_F_FORK(layout1, truncate_unhandled)
 			      LANDLOCK_ACCESS_FS_WRITE_FILE;
 	int ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, handled, rules);
 
 	ASSERT_LE(0, ruleset_fd);
@@ -3463,7 +3464,7 @@ TEST_F_FORK(layout1, truncate)
 			      LANDLOCK_ACCESS_FS_TRUNCATE;
 	int ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, handled, rules);
 
 	ASSERT_LE(0, ruleset_fd);
@@ -3690,7 +3691,7 @@ TEST_F_FORK(ftruncate, open_and_ftruncate)
 	};
 	int fd, ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
 	ASSERT_LE(0, ruleset_fd);
 	enforce_ruleset(_metadata, ruleset_fd);
@@ -3767,6 +3768,16 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes)
 	ASSERT_EQ(0, close(socket_fds[1]));
 }
 
+/* Invokes the FS_IOC_GETFLAGS IOCTL and returns its errno or 0. */
+static int test_fs_ioc_getflags_ioctl(int fd)
+{
+	uint32_t flags;
+
+	if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0)
+		return errno;
+	return 0;
+}
+
 TEST(memfd_ftruncate)
 {
 	int fd;
@@ -3783,6 +3794,412 @@ TEST(memfd_ftruncate)
 	ASSERT_EQ(0, close(fd));
 }
 
+/* clang-format off */
+FIXTURE(ioctl) {};
+/* clang-format on */
+
+FIXTURE_SETUP(ioctl)
+{
+	prepare_layout(_metadata);
+	create_file(_metadata, file1_s1d1);
+}
+
+FIXTURE_TEARDOWN(ioctl)
+{
+	EXPECT_EQ(0, remove_path(file1_s1d1));
+	cleanup_layout(_metadata);
+}
+
+FIXTURE_VARIANT(ioctl)
+{
+	const __u64 handled;
+	const __u64 permitted;
+	const mode_t open_mode;
+	/*
+	 * These are the expected IOCTL results for a representative IOCTL from
+	 * each of the IOCTL groups.  We only distinguish the 0 and EACCES
+	 * results here, and treat other errors as 0.
+	 */
+	const int expected_fioqsize_result; /* G1 */
+	const int expected_fibmap_result; /* G2 */
+	const int expected_fionread_result; /* G3 */
+	const int expected_fs_ioc_zero_range_result; /* G4 */
+	const int expected_fs_ioc_getflags_result; /* other */
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_none) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_EXECUTE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,
+	.open_mode = O_RDWR,
+	.expected_fioqsize_result = EACCES,
+	.expected_fibmap_result = EACCES,
+	.expected_fionread_result = EACCES,
+	.expected_fs_ioc_zero_range_result = EACCES,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_i) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_IOCTL,
+	.open_mode = O_RDWR,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_unhandled) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_EXECUTE,
+	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,
+	.open_mode = O_RDWR,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwd_permitted_r) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_READ_DIR,
+	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
+	.open_mode = O_RDONLY,
+	/* If LANDLOCK_ACCESS_FS_IOCTL is not handled, all IOCTLs work. */
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwd_permitted_w) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_READ_DIR,
+	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
+	.open_mode = O_WRONLY,
+	/* If LANDLOCK_ACCESS_FS_IOCTL is not handled, all IOCTLs work. */
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_ri_permitted_r) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
+	.open_mode = O_RDONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = EACCES,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_wi_permitted_w) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
+	.open_mode = O_WRONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = EACCES,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_di_permitted_d) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_DIR | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_READ_DIR,
+	.open_mode = O_RDWR,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = EACCES,
+	.expected_fionread_result = EACCES,
+	.expected_fs_ioc_zero_range_result = EACCES,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_rw) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_READ_FILE |
+		     LANDLOCK_ACCESS_FS_WRITE_FILE,
+	.open_mode = O_RDWR,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_r) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
+	.open_mode = O_RDONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = EACCES,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_ri) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.open_mode = O_RDONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = 0,
+	.expected_fs_ioc_zero_range_result = EACCES,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_w) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
+	.open_mode = O_WRONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = EACCES,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_wi) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
+		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
+	.open_mode = O_WRONLY,
+	.expected_fioqsize_result = 0,
+	.expected_fibmap_result = 0,
+	.expected_fionread_result = EACCES,
+	.expected_fs_ioc_zero_range_result = 0,
+	.expected_fs_ioc_getflags_result = 0,
+};
+
+static int test_fioqsize_ioctl(int fd)
+{
+	size_t sz;
+
+	if (ioctl(fd, FIOQSIZE, &sz) < 0)
+		return errno;
+	return 0;
+}
+
+static int test_fibmap_ioctl(int fd)
+{
+	int blk = 0;
+
+	/*
+	 * We only want to distinguish here whether Landlock already caught it,
+	 * so we treat anything but EACCESS as success.  (It commonly returns
+	 * EPERM when missing CAP_SYS_RAWIO.)
+	 */
+	if (ioctl(fd, FIBMAP, &blk) < 0 && errno == EACCES)
+		return errno;
+	return 0;
+}
+
+static int test_fionread_ioctl(int fd)
+{
+	size_t sz = 0;
+
+	if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
+		return errno;
+	return 0;
+}
+
+#define FS_IOC_ZERO_RANGE _IOW('X', 57, struct space_resv)
+
+static int test_fs_ioc_zero_range_ioctl(int fd)
+{
+	struct space_resv {
+		__s16 l_type;
+		__s16 l_whence;
+		__s64 l_start;
+		__s64 l_len; /* len == 0 means until end of file */
+		__s32 l_sysid;
+		__u32 l_pid;
+		__s32 l_pad[4]; /* reserved area */
+	} reservation = {};
+	/*
+	 * This can fail for various reasons, but we only want to distinguish
+	 * here whether Landlock already caught it, so we treat anything but
+	 * EACCES as success.
+	 */
+	if (ioctl(fd, FS_IOC_ZERO_RANGE, &reservation) < 0 && errno == EACCES)
+		return errno;
+	return 0;
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_file)
+{
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = dir_s1d1,
+			.access = variant->permitted,
+		},
+		{},
+	};
+	int fd, ruleset_fd;
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	fd = open(file1_s1d1, variant->open_mode);
+	ASSERT_LE(0, fd);
+
+	/*
+	 * Checks that IOCTL commands in each IOCTL group return the expected
+	 * errors.
+	 */
+	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
+	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
+	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
+		  test_fs_ioc_zero_range_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
+		  test_fs_ioc_getflags_ioctl(fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
+
+	ASSERT_EQ(0, close(fd));
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_dir)
+{
+	const char *const path = dir_s1d1;
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = path,
+			.access = variant->permitted,
+		},
+		{},
+	};
+	int fd, ruleset_fd;
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Ignore variant->open_mode for this test, as we intend to open a
+	 * directory.  If the directory can not be opened, the variant is
+	 * infeasible to test with an opened directory.
+	 */
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return;
+
+	/*
+	 * Checks that IOCTL commands in each IOCTL group return the expected
+	 * errors.
+	 */
+	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
+	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
+	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
+		  test_fs_ioc_zero_range_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
+		  test_fs_ioc_getflags_ioctl(fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
+
+	ASSERT_EQ(0, close(fd));
+}
+
+TEST_F_FORK(ioctl, handle_file_access_file)
+{
+	const char *const path = file1_s1d1;
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = path,
+			.access = variant->permitted,
+		},
+		{},
+	};
+	int fd, ruleset_fd;
+
+	if (variant->permitted & LANDLOCK_ACCESS_FS_READ_DIR) {
+		/* This access right can not be granted on files. */
+		return;
+	}
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	fd = open(path, variant->open_mode);
+	ASSERT_LE(0, fd);
+
+	/*
+	 * Checks that IOCTL commands in each IOCTL group return the expected
+	 * errors.
+	 */
+	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
+	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
+	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
+		  test_fs_ioc_zero_range_ioctl(fd));
+	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
+		  test_fs_ioc_getflags_ioctl(fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
+
+	ASSERT_EQ(0, close(fd));
+}
+
 /* clang-format off */
 FIXTURE(layout1_bind) {};
 /* clang-format on */
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 4/7] selftests/landlock: Test IOCTL with memfds

[Günther Noack]

Because the LANDLOCK_ACCESS_FS_IOCTL right is associated with the
opened file during open(2), IOCTLs are supposed to work with files
which are opened by means other than open(2).

Signed-off-by: Günther Noack <gnoack@google.com>
---
 tools/testing/selftests/landlock/fs_test.c | 36 ++++++++++++++++------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 564e73087e08..8a244c9cd030 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3778,20 +3778,38 @@ static int test_fs_ioc_getflags_ioctl(int fd)
 	return 0;
 }
 
-TEST(memfd_ftruncate)
+TEST(memfd_ftruncate_and_ioctl)
 {
-	int fd;
-
-	fd = memfd_create("name", MFD_CLOEXEC);
-	ASSERT_LE(0, fd);
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = ACCESS_ALL,
+	};
+	int ruleset_fd, fd, i;
 
 	/*
-	 * Checks that ftruncate is permitted on file descriptors that are
-	 * created in ways other than open(2).
+	 * We exercise the same test both with and without Landlock enabled, to
+	 * ensure that it behaves the same in both cases.
 	 */
-	EXPECT_EQ(0, test_ftruncate(fd));
+	for (i = 0; i < 2; i++) {
+		/* Creates a new memfd. */
+		fd = memfd_create("name", MFD_CLOEXEC);
+		ASSERT_LE(0, fd);
 
-	ASSERT_EQ(0, close(fd));
+		/*
+		 * Checks that operations associated with the opened file
+		 * (ftruncate, ioctl) are permitted on file descriptors that are
+		 * created in ways other than open(2).
+		 */
+		EXPECT_EQ(0, test_ftruncate(fd));
+		EXPECT_EQ(0, test_fs_ioc_getflags_ioctl(fd));
+
+		ASSERT_EQ(0, close(fd));
+
+		/* Enables Landlock. */
+		ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+		ASSERT_LE(0, ruleset_fd);
+		enforce_ruleset(_metadata, ruleset_fd);
+		ASSERT_EQ(0, close(ruleset_fd));
+	}
 }
 
 /* clang-format off */
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 5/7] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH)

[Günther Noack]

ioctl(2) and ftruncate(2) operations on files opened with O_PATH
should always return EBADF, independent of the
LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL access rights
in that file hierarchy.

Signed-off-by: Günther Noack <gnoack@google.com>
Suggested-by: Mickaël Salaün <mic@digikod.net>
---
 tools/testing/selftests/landlock/fs_test.c | 40 ++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 8a244c9cd030..06c47c816c51 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3812,6 +3812,46 @@ TEST(memfd_ftruncate_and_ioctl)
 	}
 }
 
+TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl)
+{
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = ACCESS_ALL,
+	};
+	int ruleset_fd, fd;
+
+	/*
+	 * Checks that for files opened with O_PATH, both ioctl(2) and
+	 * ftruncate(2) yield EBADF, as it is documented in open(2) for the
+	 * O_PATH flag.
+	 */
+	fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+
+	EXPECT_EQ(EBADF, test_ftruncate(fd));
+	EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+	ASSERT_EQ(0, close(fd));
+
+	/* Enables Landlock. */
+	ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Checks that after enabling Landlock,
+	 * - the file can still be opened with O_PATH
+	 * - both ioctl and truncate still yield EBADF (not EACCES).
+	 */
+	fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+
+	EXPECT_EQ(EBADF, test_ftruncate(fd));
+	EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+	ASSERT_EQ(0, close(fd));
+}
+
 /* clang-format off */
 FIXTURE(ioctl) {};
 /* clang-format on */
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 6/7] samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL

[Günther Noack]

Add ioctl support to the Landlock sample tool.

The ioctl right is grouped with the read-write rights in the sample
tool, as some ioctl requests provide features that mutate state.

Signed-off-by: Günther Noack <gnoack@google.com>
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
 samples/landlock/sandboxer.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 08596c0ef070..d7323e5526be 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -81,7 +81,8 @@ static int parse_path(char *env_path, const char ***const path_list)
 	LANDLOCK_ACCESS_FS_EXECUTE | \
 	LANDLOCK_ACCESS_FS_WRITE_FILE | \
 	LANDLOCK_ACCESS_FS_READ_FILE | \
-	LANDLOCK_ACCESS_FS_TRUNCATE)
+	LANDLOCK_ACCESS_FS_TRUNCATE | \
+	LANDLOCK_ACCESS_FS_IOCTL)
 
 /* clang-format on */
 
@@ -199,11 +200,12 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
 	LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
 	LANDLOCK_ACCESS_FS_MAKE_SYM | \
 	LANDLOCK_ACCESS_FS_REFER | \
-	LANDLOCK_ACCESS_FS_TRUNCATE)
+	LANDLOCK_ACCESS_FS_TRUNCATE | \
+	LANDLOCK_ACCESS_FS_IOCTL)
 
 /* clang-format on */
 
-#define LANDLOCK_ABI_LAST 4
+#define LANDLOCK_ABI_LAST 5
 
 int main(const int argc, char *const argv[], char *const *const envp)
 {
@@ -317,6 +319,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
 		ruleset_attr.handled_access_net &=
 			~(LANDLOCK_ACCESS_NET_BIND_TCP |
 			  LANDLOCK_ACCESS_NET_CONNECT_TCP);
+		__attribute__((fallthrough));
+	case 4:
+		/* Removes LANDLOCK_ACCESS_FS_IOCTL for ABI < 5 */
+		ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL;
+
 		fprintf(stderr,
 			"Hint: You should update the running kernel "
 			"to leverage Landlock features "
-- 
2.43.0.rc1.413.gea7ed67945-goog

[PATCH v5 7/7] landlock: Document IOCTL support

[Günther Noack]

In the paragraph above the fallback logic, use the shorter phrasing
from the landlock(7) man page.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 Documentation/userspace-api/landlock.rst | 74 +++++++++++++++++++-----
 1 file changed, 59 insertions(+), 15 deletions(-)

diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 2e3822677061..68498ca64dc9 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -75,7 +75,8 @@ to be explicit about the denied-by-default access rights.
             LANDLOCK_ACCESS_FS_MAKE_BLOCK |
             LANDLOCK_ACCESS_FS_MAKE_SYM |
             LANDLOCK_ACCESS_FS_REFER |
-            LANDLOCK_ACCESS_FS_TRUNCATE,
+            LANDLOCK_ACCESS_FS_TRUNCATE |
+            LANDLOCK_ACCESS_FS_IOCTL,
         .handled_access_net =
             LANDLOCK_ACCESS_NET_BIND_TCP |
             LANDLOCK_ACCESS_NET_CONNECT_TCP,
@@ -84,10 +85,10 @@ to be explicit about the denied-by-default access rights.
 Because we may not know on which kernel version an application will be
 executed, it is safer to follow a best-effort security approach.  Indeed, we
 should try to protect users as much as possible whatever the kernel they are
-using.  To avoid binary enforcement (i.e. either all security features or
-none), we can leverage a dedicated Landlock command to get the current version
-of the Landlock ABI and adapt the handled accesses.  Let's check if we should
-remove access rights which are only supported in higher versions of the ABI.
+using.
+
+To be compatible with older Linux versions, we detect the available Landlock ABI
+version, and only use the available subset of access rights:
 
 .. code-block:: c
 
@@ -113,6 +114,10 @@ remove access rights which are only supported in higher versions of the ABI.
         ruleset_attr.handled_access_net &=
             ~(LANDLOCK_ACCESS_NET_BIND_TCP |
               LANDLOCK_ACCESS_NET_CONNECT_TCP);
+        __attribute__((fallthrough));
+    case 4:
+        /* Removes LANDLOCK_ACCESS_FS_IOCTL for ABI < 5 */
+        ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL;
     }
 
 This enables to create an inclusive ruleset that will contain our rules.
@@ -224,6 +229,7 @@ access rights per directory enables to change the location of such directory
 without relying on the destination directory access rights (except those that
 are required for this operation, see ``LANDLOCK_ACCESS_FS_REFER``
 documentation).
+
 Having self-sufficient hierarchies also helps to tighten the required access
 rights to the minimal set of data.  This also helps avoid sinkhole directories,
 i.e.  directories where data can be linked to but not linked from.  However,
@@ -317,18 +323,24 @@ It should also be noted that truncating files does not require the
 system call, this can also be done through :manpage:`open(2)` with the flags
 ``O_RDONLY | O_TRUNC``.
 
-When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE``
-right is associated with the newly created file descriptor and will be used for
-subsequent truncation attempts using :manpage:`ftruncate(2)`.  The behavior is
-similar to opening a file for reading or writing, where permissions are checked
-during :manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and
+The truncate right is associated with the opened file (see below).
+
+Rights associated with file descriptors
+---------------------------------------
+
+When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE`` and
+``LANDLOCK_ACCESS_FS_IOCTL`` rights is associated with the newly created file
+descriptor and will be used for subsequent truncation and ioctl attempts using
+:manpage:`ftruncate(2)` and :manpage:`ioctl(2)`.  The behavior is similar to
+opening a file for reading or writing, where permissions are checked during
+:manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and
 :manpage:`write(2)` calls.
 
-As a consequence, it is possible to have multiple open file descriptors for the
-same file, where one grants the right to truncate the file and the other does
-not.  It is also possible to pass such file descriptors between processes,
-keeping their Landlock properties, even when these processes do not have an
-enforced Landlock ruleset.
+As a consequence, it is possible to have multiple open file descriptors
+referring to the same file, where one grants the truncate or ioctl right and the
+other does not.  It is also possible to pass such file descriptors between
+processes, keeping their Landlock properties, even when these processes do not
+have an enforced Landlock ruleset.
 
 Compatibility
 =============
@@ -457,6 +469,28 @@ Memory usage
 Kernel memory allocated to create rulesets is accounted and can be restricted
 by the Documentation/admin-guide/cgroup-v1/memory.rst.
 
+IOCTL support
+-------------
+
+The ``LANDLOCK_ACCESS_FS_IOCTL`` access right restricts the use of
+:manpage:`ioctl(2)`, but it only applies to newly opened files.  This means
+specifically that pre-existing file descriptors like stdin, stdout and stderr
+are unaffected.
+
+Users should be aware that TTY devices have traditionally permitted to control
+other processes on the same TTY through the ``TIOCSTI`` and ``TIOCLINUX`` IOCTL
+commands.  It is therefore recommended to close inherited TTY file descriptors,
+or to reopen them from ``/proc/self/fd/*`` without the
+``LANDLOCK_ACCESS_FS_IOCTL`` right, if possible.  The :manpage:`isatty(3)`
+function checks whether a given file descriptor is a TTY.
+
+Landlock's IOCTL support is coarse-grained at the moment, but may become more
+fine-grained in the future.  Until then, users are advised to establish the
+guarantees that they need through the file hierarchy, by only permitting the
+``LANDLOCK_ACCESS_FS_IOCTL`` right on files where it is really harmless.  In
+cases where you can control the mounts, the ``nodev`` mount option can help to
+rule out that device files can be accessed.
+
 Previous limitations
 ====================
 
@@ -494,6 +528,16 @@ bind and connect actions to only a set of allowed ports thanks to the new
 ``LANDLOCK_ACCESS_NET_BIND_TCP`` and ``LANDLOCK_ACCESS_NET_CONNECT_TCP``
 access rights.
 
+IOCTL (ABI < 5)
+---------------
+
+IOCTL operations could not be denied before the fifth Landlock ABI, so
+:manpage:`ioctl(2)` is always allowed when using a kernel that only supports an
+earlier ABI.
+
+Starting with the Landlock ABI version 5, it is possible to restrict the use of
+:manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL`` access right.
+
 .. _kernel_support:
 
 Kernel support
-- 
2.43.0.rc1.413.gea7ed67945-goog

Re: [PATCH v5 2/7] landlock: Add IOCTL access right

[Mickaël Salaün]

On Fri, Nov 17, 2023 at 04:49:15PM +0100, Günther Noack wrote:
> Introduces the LANDLOCK_ACCESS_FS_IOCTL access right
> and increments the Landlock ABI version to 5.
> 
> Like the truncate right, these rights are associated with a file
> descriptor at the time of open(2), and get respected even when the
> file descriptor is used outside of the thread which it was originally
> opened in.
> 
> A newly enabled Landlock policy therefore does not apply to file
> descriptors which are already open.
> 
> If the LANDLOCK_ACCESS_FS_IOCTL right is handled, only a small number
> of safe IOCTL commands will be permitted on newly opened files.  The
> permitted IOCTLs can be configured through the ruleset in limited ways
> now.  (See documentation for details.)
> 
> Noteworthy scenarios which require special attention:
> 
> TTY devices support IOCTLs like TIOCSTI and TIOCLINUX, which can be
> used to control shell processes on the same terminal which run at
> different privilege levels, which may make it possible to escape a
> sandbox.  Because stdin, stdout and stderr are normally inherited
> rather than newly opened, IOCTLs are usually permitted on them even
> after the Landlock policy is enforced.
> 
> Some legitimate file system features, like setting up fscrypt, are
> exposed as IOCTL commands on regular files and directories -- users of
> Landlock are advised to double check that the sandboxed process does
> not need to invoke these IOCTLs.
> 
> Known limitations:
> 
> The LANDLOCK_ACCESS_FS_IOCTL access right is a coarse-grained control
> over IOCTL commands.  Future work will enable a more fine-grained
> access control for IOCTLs.
> 
> In the meantime, Landlock users may use path-based restrictions in
> combination with their knowledge about the file system layout to
> control what IOCTLs can be done.  Mounting file systems with the nodev
> option can help to distinguish regular files and devices, and give
> guarantees about the affected files, which Landlock alone can not give
> yet.
> 
> Signed-off-by: Günther Noack <gnoack@google.com>
> ---
>  include/uapi/linux/landlock.h                |  58 ++++++-
>  security/landlock/fs.c                       | 150 ++++++++++++++++++-
>  security/landlock/fs.h                       |  11 ++
>  security/landlock/limits.h                   |  15 +-
>  security/landlock/ruleset.h                  |   2 +-
>  security/landlock/syscalls.c                 |  10 +-
>  tools/testing/selftests/landlock/base_test.c |   2 +-
>  tools/testing/selftests/landlock/fs_test.c   |   5 +-
>  8 files changed, 233 insertions(+), 20 deletions(-)
> 
> diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
> index 25c8d7677539..578f268b084b 100644
> --- a/include/uapi/linux/landlock.h
> +++ b/include/uapi/linux/landlock.h
> @@ -128,7 +128,7 @@ struct landlock_net_port_attr {
>   * files and directories.  Files or directories opened before the sandboxing
>   * are not subject to these restrictions.
>   *
> - * A file can only receive these access rights:
> + * The following access rights apply only to files:
>   *
>   * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
>   * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that
> @@ -138,12 +138,13 @@ struct landlock_net_port_attr {
>   * - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access.
>   * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`,
>   *   :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with
> - *   ``O_TRUNC``. Whether an opened file can be truncated with
> - *   :manpage:`ftruncate(2)` is determined during :manpage:`open(2)`, in the
> - *   same way as read and write permissions are checked during
> - *   :manpage:`open(2)` using %LANDLOCK_ACCESS_FS_READ_FILE and
> - *   %LANDLOCK_ACCESS_FS_WRITE_FILE. This access right is available since the
> - *   third version of the Landlock ABI.
> + *   ``O_TRUNC``.  This access right is available since the third version of the
> + *   Landlock ABI.
> + *
> + * Whether an opened file can be truncated with :manpage:`ftruncate(2)` or used
> + * with `ioctl(2)` is determined during :manpage:`open(2)`, in the same way as
> + * read and write permissions are checked during :manpage:`open(2)` using
> + * %LANDLOCK_ACCESS_FS_READ_FILE and %LANDLOCK_ACCESS_FS_WRITE_FILE.
>   *
>   * A directory can receive access rights related to files or directories.  The
>   * following access right is applied to the directory itself, and the
> @@ -198,13 +199,53 @@ struct landlock_net_port_attr {
>   *   If multiple requirements are not met, the ``EACCES`` error code takes
>   *   precedence over ``EXDEV``.
>   *
> + * The following access right applies both to files and directories:
> + *
> + * - %LANDLOCK_ACCESS_FS_IOCTL: Invoke :manpage:`ioctl(2)` commands on an opened
> + *   file or directory.
> + *
> + *   This access right applies to all :manpage:`ioctl(2)` commands, except of
> + *   ``FIOCLEX``, ``FIONCLEX``, ``FIONBIO`` and ``FIOASYNC``.  These commands
> + *   continue to be invokable independent of the %LANDLOCK_ACCESS_FS_IOCTL
> + *   access right.
> + *
> + *   When certain other access rights are handled in the ruleset, in addition to
> + *   %LANDLOCK_ACCESS_FS_IOCTL, granting these access rights will unlock access
> + *   to additional groups of IOCTL commands, on the affected files:
> + *
> + *   * %LANDLOCK_ACCESS_FS_READ_FILE unlocks access to ``FIOQSIZE``,
> + *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``, ``FIONREAD``,
> + *     ``FIDEDUPRANGE``.
> + *
> + *   * %LANDLOCK_ACCESS_FS_WRITE_FILE unlocks access to ``FIOQSIZE``,
> + *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``, ``FICLONE``,
> + *     ``FICLONERANGE``, ``FS_IOC_RESVSP``, ``FS_IOC_RESVSP64``,
> + *     ``FS_IOC_UNRESVSP``, ``FS_IOC_UNRESVSP64``, ``FS_IOC_ZERO_RANGE``.
> + *
> + *   * %LANDLOCK_ACCESS_FS_READ_DIR unlocks access to ``FIOQSIZE``,
> + *     ``FS_IOC_FIEMAP``, ``FIBMAP``, ``FIGETBSZ``.
> + *
> + *   When these access rights are handled in the ruleset, the availability of
> + *   the affected IOCTL commands is not governed by %LANDLOCK_ACCESS_FS_IOCTL
> + *   any more, but by the respective access right.
> + *
> + *   All other IOCTL commands are not handled specially, and are governed by
> + *   %LANDLOCK_ACCESS_FS_IOCTL.  This includes %FS_IOC_GETFLAGS and
> + *   %FS_IOC_SETFLAGS for manipulating inode flags (:manpage:`ioctl_iflags(2)`),
> + *   %FS_IOC_FSFETXATTR and %FS_IOC_FSSETXATTR for manipulating extended
> + *   attributes, as well as %FIFREEZE and %FITHAW for freezing and thawing file
> + *   systems.
> + *
> + *   This access right is available since the fifth version of the Landlock
> + *   ABI.
> + *
>   * .. warning::
>   *
>   *   It is currently not possible to restrict some file-related actions
>   *   accessible through these syscall families: :manpage:`chdir(2)`,
>   *   :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`chmod(2)`,
>   *   :manpage:`chown(2)`, :manpage:`setxattr(2)`, :manpage:`utime(2)`,
> - *   :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, :manpage:`access(2)`.
> + *   :manpage:`fcntl(2)`, :manpage:`access(2)`.
>   *   Future Landlock evolutions will enable to restrict them.
>   */
>  /* clang-format off */
> @@ -223,6 +264,7 @@ struct landlock_net_port_attr {
>  #define LANDLOCK_ACCESS_FS_MAKE_SYM			(1ULL << 12)
>  #define LANDLOCK_ACCESS_FS_REFER			(1ULL << 13)
>  #define LANDLOCK_ACCESS_FS_TRUNCATE			(1ULL << 14)
> +#define LANDLOCK_ACCESS_FS_IOCTL			(1ULL << 15)
>  /* clang-format on */
>  
>  /**
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index bc7c126deea2..4d305ddcbc57 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -7,12 +7,14 @@
>   * Copyright © 2021-2022 Microsoft Corporation
>   */
>  
> +#include <asm/ioctls.h>
>  #include <linux/atomic.h>
>  #include <linux/bitops.h>
>  #include <linux/bits.h>
>  #include <linux/compiler_types.h>
>  #include <linux/dcache.h>
>  #include <linux/err.h>
> +#include <linux/falloc.h>
>  #include <linux/fs.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
> @@ -28,6 +30,7 @@
>  #include <linux/types.h>
>  #include <linux/wait_bit.h>
>  #include <linux/workqueue.h>
> +#include <uapi/linux/fiemap.h>
>  #include <uapi/linux/landlock.h>
>  
>  #include "common.h"
> @@ -83,6 +86,68 @@ static const struct landlock_object_underops landlock_fs_underops = {
>  	.release = release_inode
>  };
>  
> +/* IOCTL helpers */
> +
> +/**
> + * expand_ioctl() - Return the dst flags from either the src flag or the
> + * %LANDLOCK_ACCESS_FS_IOCTL flag, depending on whether the
> + * %LANDLOCK_ACCESS_FS_IOCTL and src access rights are handled or not.
> + *
> + * @handled: Handled access rights
> + * @access: The access mask to copy values from
> + * @src: A single access right to copy from in @access.
> + * @dst: One or more access rights to copy to
> + *
> + * Returns: @dst, or 0
> + */
> +static inline access_mask_t expand_ioctl(const access_mask_t handled,

Please remove all explicit inlines in the .c files, the compiler should
be able to inline them if necessary, or it my not inline them at all
anyway.  It would be nice to check the -O2 code to see what GCC or clang
do though, and I guess they will inline this kind of pattern.

> +					 const access_mask_t access,
> +					 const access_mask_t src,
> +					 const access_mask_t dst)
> +{
> +	if (!(handled & LANDLOCK_ACCESS_FS_IOCTL))
> +		return 0;
> +
> +	access_mask_t copy_from = (handled & src) ? src :

Please declare variables at the beginning of blocks.

> +						    LANDLOCK_ACCESS_FS_IOCTL;
> +	if (access & copy_from)
> +		return dst;
> +
> +	return 0;
> +}
> +
> +/**
> + * landlock_expand_access_fs() - Returns @access with the synthetic IOCTL group
> + * flags enabled if necessary.
> + *
> + * @handled: Handled FS access rights.
> + * @access: FS access rights to expand.
> + *
> + * Returns: @access expanded by the necessary flags for the synthetic IOCTL
> + * access rights.
> + */
> +static inline access_mask_t
> +landlock_expand_access_fs(const access_mask_t handled,
> +			  const access_mask_t access)
> +{
> +	return access |
> +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_WRITE_FILE,
> +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
> +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
> +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP4) |
> +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_FILE,
> +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
> +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
> +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP3) |
> +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_DIR,
> +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1);
> +}

I'd prefer to keep the semantic definition of these groups (i.e.
required_ioctl_access) close the definition of access right expantions,
and also close to the ioctl_groups veriable. Actually, ioctl_groups
might make more sense close to the group definition, and then probably
another define... What do you think?

> +
> +access_mask_t landlock_expand_handled_access_fs(const access_mask_t handled)
> +{
> +	return landlock_expand_access_fs(handled, handled);
> +}
> +
>  /* Ruleset management */
>  
>  static struct landlock_object *get_inode_object(struct inode *const inode)
> @@ -147,7 +212,8 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
>  	LANDLOCK_ACCESS_FS_EXECUTE | \
>  	LANDLOCK_ACCESS_FS_WRITE_FILE | \
>  	LANDLOCK_ACCESS_FS_READ_FILE | \
> -	LANDLOCK_ACCESS_FS_TRUNCATE)
> +	LANDLOCK_ACCESS_FS_TRUNCATE | \
> +	LANDLOCK_ACCESS_FS_IOCTL)
>  /* clang-format on */
>  
>  /*
> @@ -157,6 +223,7 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>  			    const struct path *const path,
>  			    access_mask_t access_rights)
>  {
> +	access_mask_t handled;
>  	int err;
>  	struct landlock_id id = {
>  		.type = LANDLOCK_KEY_INODE,
> @@ -169,9 +236,11 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>  	if (WARN_ON_ONCE(ruleset->num_layers != 1))
>  		return -EINVAL;
>  
> +	handled = landlock_get_fs_access_mask(ruleset, 0);
> +	/* Expands the synthetic IOCTL groups. */
> +	access_rights |= landlock_expand_access_fs(handled, access_rights);
>  	/* Transforms relative access rights to absolute ones. */
> -	access_rights |= LANDLOCK_MASK_ACCESS_FS &
> -			 ~landlock_get_fs_access_mask(ruleset, 0);
> +	access_rights |= LANDLOCK_MASK_ACCESS_FS & ~handled;
>  	id.key.object = get_inode_object(d_backing_inode(path->dentry));
>  	if (IS_ERR(id.key.object))
>  		return PTR_ERR(id.key.object);
> @@ -1119,11 +1188,17 @@ static int hook_file_alloc_security(struct file *const file)
>  	return 0;
>  }
>  
> +static const access_mask_t ioctl_groups =
> +	LANDLOCK_ACCESS_FS_IOCTL_GROUP1 | LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
> +	LANDLOCK_ACCESS_FS_IOCTL_GROUP3 | LANDLOCK_ACCESS_FS_IOCTL_GROUP4;
> +
>  static int hook_file_open(struct file *const file)
>  {
>  	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
>  	access_mask_t open_access_request, full_access_request, allowed_access;
> -	const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
> +	const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE |
> +					      LANDLOCK_ACCESS_FS_IOCTL |
> +					      ioctl_groups;
>  	const struct landlock_ruleset *const dom = get_current_fs_domain();
>  
>  	if (!dom)
> @@ -1196,6 +1271,72 @@ static int hook_file_truncate(struct file *const file)
>  	return -EACCES;
>  }
>  
> +/**
> + * required_ioctl_access(): Determine required IOCTL access rights.
> + *
> + * @cmd: The IOCTL command that is supposed to be run.
> + *
> + * Returns: The access rights that must be granted on an opened file in order to
> + * use the given @cmd.
> + */
> +static access_mask_t required_ioctl_access(unsigned int cmd)
> +{
> +	switch (cmd) {
> +	case FIOCLEX:
> +	case FIONCLEX:
> +	case FIONBIO:
> +	case FIOASYNC:
> +		/*
> +		 * FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC manipulate the FD's
> +		 * close-on-exec and the file's buffered-IO and async flags.
> +		 * These operations are also available through fcntl(2),
> +		 * and are unconditionally permitted in Landlock.
> +		 */
> +		return 0;
> +	case FIOQSIZE:
> +		return LANDLOCK_ACCESS_FS_IOCTL_GROUP1;
> +	case FS_IOC_FIEMAP:
> +	case FIBMAP:
> +	case FIGETBSZ:
> +		return LANDLOCK_ACCESS_FS_IOCTL_GROUP2;
> +	case FIONREAD:
> +	case FIDEDUPERANGE:
> +		return LANDLOCK_ACCESS_FS_IOCTL_GROUP3;
> +	case FICLONE:
> +	case FICLONERANGE:
> +	case FS_IOC_RESVSP:
> +	case FS_IOC_RESVSP64:
> +	case FS_IOC_UNRESVSP:
> +	case FS_IOC_UNRESVSP64:
> +	case FS_IOC_ZERO_RANGE:
> +		return LANDLOCK_ACCESS_FS_IOCTL_GROUP4;
> +	default:
> +		/*
> +		 * Other commands are guarded by the catch-all access right.
> +		 */
> +		return LANDLOCK_ACCESS_FS_IOCTL;
> +	}
> +}
> +
> +static int hook_file_ioctl(struct file *file, unsigned int cmd,
> +			   unsigned long arg)
> +{
> +	const access_mask_t required_access = required_ioctl_access(cmd);
> +	const access_mask_t allowed_access =
> +		landlock_file(file)->allowed_access;
> +
> +	/*
> +	 * It is the access rights at the time of opening the file which
> +	 * determine whether ioctl can be used on the opened file later.

s/ioctl/IOCTL/g

> +	 *
> +	 * The access right is attached to the opened file in hook_file_open().
> +	 */
> +	if ((allowed_access & required_access) == required_access)
> +		return 0;
> +
> +	return -EACCES;
> +}
> +
>  static struct security_hook_list landlock_hooks[] __ro_after_init = {
>  	LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
>  
> @@ -1218,6 +1359,7 @@ static struct security_hook_list landlock_hooks[] __ro_after_init = {
>  	LSM_HOOK_INIT(file_alloc_security, hook_file_alloc_security),
>  	LSM_HOOK_INIT(file_open, hook_file_open),
>  	LSM_HOOK_INIT(file_truncate, hook_file_truncate),
> +	LSM_HOOK_INIT(file_ioctl, hook_file_ioctl),
>  };
>  
>  __init void landlock_add_fs_hooks(void)
> diff --git a/security/landlock/fs.h b/security/landlock/fs.h
> index 488e4813680a..b3ef11968160 100644
> --- a/security/landlock/fs.h
> +++ b/security/landlock/fs.h
> @@ -92,4 +92,15 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>  			    const struct path *const path,
>  			    access_mask_t access_hierarchy);
>  
> +/**
> + * landlock_expand_handled_access_fs() - add synthetic IOCTL access rights to an
> + * access mask of handled accesses.
> + *
> + * @handled: The handled accesses of a ruleset that is being created
> + *
> + * Returns: @handled, with the bits for the synthetic IOCTL access rights set,
> + * if %LANDLOCK_ACCESS_FS_IOCTL is handled
> + */

This doc should be in fs.c

> +access_mask_t landlock_expand_handled_access_fs(const access_mask_t handled);
> +
>  #endif /* _SECURITY_LANDLOCK_FS_H */
> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
> index 93c9c6f91556..75e822f878e0 100644
> --- a/security/landlock/limits.h
> +++ b/security/landlock/limits.h
> @@ -18,7 +18,20 @@
>  #define LANDLOCK_MAX_NUM_LAYERS		16
>  #define LANDLOCK_MAX_NUM_RULES		U32_MAX
>  
> -#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_TRUNCATE
> +#define LANDLOCK_LAST_PUBLIC_ACCESS_FS	LANDLOCK_ACCESS_FS_IOCTL
> +#define LANDLOCK_MASK_PUBLIC_ACCESS_FS	((LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1) - 1)
> +
> +/*
> + * These are synthetic access rights, which are only used within the kernel, but
> + * not exposed to callers in userspace.  The mapping between these access rights
> + * and IOCTL commands is defined in the required_ioctl_access() helper function.
> + */
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP1	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP2	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 2)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP3	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 3)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP4	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 4)
> +
> +#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_IOCTL_GROUP4
>  #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
>  #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
>  #define LANDLOCK_SHIFT_ACCESS_FS	0

Re: [PATCH v5 2/7] landlock: Add IOCTL access right

[Mickaël Salaün]

On Fri, Nov 17, 2023 at 04:49:15PM +0100, Günther Noack wrote:
> Introduces the LANDLOCK_ACCESS_FS_IOCTL access right
> and increments the Landlock ABI version to 5.
> 
> Like the truncate right, these rights are associated with a file
> descriptor at the time of open(2), and get respected even when the
> file descriptor is used outside of the thread which it was originally
> opened in.
> 
> A newly enabled Landlock policy therefore does not apply to file
> descriptors which are already open.
> 
> If the LANDLOCK_ACCESS_FS_IOCTL right is handled, only a small number
> of safe IOCTL commands will be permitted on newly opened files.  The
> permitted IOCTLs can be configured through the ruleset in limited ways
> now.  (See documentation for details.)
> 
> Noteworthy scenarios which require special attention:
> 
> TTY devices support IOCTLs like TIOCSTI and TIOCLINUX, which can be
> used to control shell processes on the same terminal which run at
> different privilege levels, which may make it possible to escape a
> sandbox.  Because stdin, stdout and stderr are normally inherited
> rather than newly opened, IOCTLs are usually permitted on them even
> after the Landlock policy is enforced.
> 
> Some legitimate file system features, like setting up fscrypt, are
> exposed as IOCTL commands on regular files and directories -- users of
> Landlock are advised to double check that the sandboxed process does
> not need to invoke these IOCTLs.
> 
> Known limitations:
> 
> The LANDLOCK_ACCESS_FS_IOCTL access right is a coarse-grained control
> over IOCTL commands.  Future work will enable a more fine-grained
> access control for IOCTLs.
> 
> In the meantime, Landlock users may use path-based restrictions in
> combination with their knowledge about the file system layout to
> control what IOCTLs can be done.  Mounting file systems with the nodev
> option can help to distinguish regular files and devices, and give
> guarantees about the affected files, which Landlock alone can not give
> yet.
> 
> Signed-off-by: Günther Noack <gnoack@google.com>
> ---
>  include/uapi/linux/landlock.h                |  58 ++++++-
>  security/landlock/fs.c                       | 150 ++++++++++++++++++-
>  security/landlock/fs.h                       |  11 ++
>  security/landlock/limits.h                   |  15 +-
>  security/landlock/ruleset.h                  |   2 +-
>  security/landlock/syscalls.c                 |  10 +-
>  tools/testing/selftests/landlock/base_test.c |   2 +-
>  tools/testing/selftests/landlock/fs_test.c   |   5 +-
>  8 files changed, 233 insertions(+), 20 deletions(-)
> 

> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
> index 93c9c6f91556..75e822f878e0 100644
> --- a/security/landlock/limits.h
> +++ b/security/landlock/limits.h
> @@ -18,7 +18,20 @@
>  #define LANDLOCK_MAX_NUM_LAYERS		16
>  #define LANDLOCK_MAX_NUM_RULES		U32_MAX
>  
> -#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_TRUNCATE
> +#define LANDLOCK_LAST_PUBLIC_ACCESS_FS	LANDLOCK_ACCESS_FS_IOCTL
> +#define LANDLOCK_MASK_PUBLIC_ACCESS_FS	((LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1) - 1)
> +
> +/*
> + * These are synthetic access rights, which are only used within the kernel, but
> + * not exposed to callers in userspace.  The mapping between these access rights
> + * and IOCTL commands is defined in the required_ioctl_access() helper function.
> + */
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP1	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP2	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 2)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP3	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 3)
> +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP4	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 4)

Please move this LANDLOCK_ACCESS_FS_IOCTL_* block to fs.h

We can still create the public and private masks in limits.h but add a
static_assert() to make sure there is no overlap.

> +
> +#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_IOCTL_GROUP4
>  #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
>  #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
>  #define LANDLOCK_SHIFT_ACCESS_FS	0
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index c7f1526784fd..5a28ea8e1c3d 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -30,7 +30,7 @@
>  	LANDLOCK_ACCESS_FS_REFER)
>  /* clang-format on */
>  
> -typedef u16 access_mask_t;
> +typedef u32 access_mask_t;
>  /* Makes sure all filesystem access rights can be stored. */
>  static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
>  /* Makes sure all network access rights can be stored. */
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 898358f57fa0..c196cac2a5fb 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -137,7 +137,7 @@ static const struct file_operations ruleset_fops = {
>  	.write = fop_dummy_write,
>  };
>  
> -#define LANDLOCK_ABI_VERSION 4
> +#define LANDLOCK_ABI_VERSION 5
>  
>  /**
>   * sys_landlock_create_ruleset - Create a new ruleset
> @@ -192,8 +192,8 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
>  		return err;
>  
>  	/* Checks content (and 32-bits cast). */
> -	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
> -	    LANDLOCK_MASK_ACCESS_FS)
> +	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_PUBLIC_ACCESS_FS) !=
> +	    LANDLOCK_MASK_PUBLIC_ACCESS_FS)

It would now be possible to add LANDLOCK_ACCESS_FS_IOCTL_GROUP* to a
rule, which is not part of the API/ABI. I've sent a patch with new tests
to make sure this is covered:
https://lore.kernel.org/r/20231120193914.441117-2-mic@digikod.net

I'll push it in my -next branch if everything is OK before pushing your
next series. Please review it.

>  		return -EINVAL;
>  

Re: [PATCH v5 3/7] selftests/landlock: Test IOCTL support

[Mickaël Salaün]

On Fri, Nov 17, 2023 at 04:49:16PM +0100, Günther Noack wrote:
> Exercises Landlock's IOCTL feature in different combinations of
> handling and permitting the rights LANDLOCK_ACCESS_FS_IOCTL,
> LANDLOCK_ACCESS_FS_READ_FILE, LANDLOCK_ACCESS_FS_WRITE_FILE and
> LANDLOCK_ACCESS_FS_READ_DIR, and in different combinations of using
> files and directories.
> 
> Signed-off-by: Günther Noack <gnoack@google.com>
> ---
>  tools/testing/selftests/landlock/fs_test.c | 423 ++++++++++++++++++++-
>  1 file changed, 420 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
> index 256cd9a96eb7..564e73087e08 100644
> --- a/tools/testing/selftests/landlock/fs_test.c
> +++ b/tools/testing/selftests/landlock/fs_test.c
> @@ -9,6 +9,7 @@
>  
>  #define _GNU_SOURCE
>  #include <fcntl.h>
> +#include <linux/fs.h>
>  #include <linux/landlock.h>
>  #include <linux/magic.h>
>  #include <sched.h>
> @@ -3380,7 +3381,7 @@ TEST_F_FORK(layout1, truncate_unhandled)
>  			      LANDLOCK_ACCESS_FS_WRITE_FILE;
>  	int ruleset_fd;
>  
> -	/* Enable Landlock. */
> +	/* Enables Landlock. */
>  	ruleset_fd = create_ruleset(_metadata, handled, rules);
>  
>  	ASSERT_LE(0, ruleset_fd);
> @@ -3463,7 +3464,7 @@ TEST_F_FORK(layout1, truncate)
>  			      LANDLOCK_ACCESS_FS_TRUNCATE;
>  	int ruleset_fd;
>  
> -	/* Enable Landlock. */
> +	/* Enables Landlock. */
>  	ruleset_fd = create_ruleset(_metadata, handled, rules);
>  
>  	ASSERT_LE(0, ruleset_fd);
> @@ -3690,7 +3691,7 @@ TEST_F_FORK(ftruncate, open_and_ftruncate)
>  	};
>  	int fd, ruleset_fd;
>  
> -	/* Enable Landlock. */
> +	/* Enables Landlock. */
>  	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
>  	ASSERT_LE(0, ruleset_fd);
>  	enforce_ruleset(_metadata, ruleset_fd);
> @@ -3767,6 +3768,16 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes)
>  	ASSERT_EQ(0, close(socket_fds[1]));
>  }
>  
> +/* Invokes the FS_IOC_GETFLAGS IOCTL and returns its errno or 0. */
> +static int test_fs_ioc_getflags_ioctl(int fd)
> +{
> +	uint32_t flags;
> +
> +	if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0)
> +		return errno;
> +	return 0;
> +}
> +
>  TEST(memfd_ftruncate)
>  {
>  	int fd;
> @@ -3783,6 +3794,412 @@ TEST(memfd_ftruncate)
>  	ASSERT_EQ(0, close(fd));
>  }
>  
> +/* clang-format off */
> +FIXTURE(ioctl) {};
> +/* clang-format on */
> +
> +FIXTURE_SETUP(ioctl)
> +{
> +	prepare_layout(_metadata);
> +	create_file(_metadata, file1_s1d1);
> +}
> +
> +FIXTURE_TEARDOWN(ioctl)
> +{
> +	EXPECT_EQ(0, remove_path(file1_s1d1));
> +	cleanup_layout(_metadata);
> +}
> +
> +FIXTURE_VARIANT(ioctl)
> +{
> +	const __u64 handled;
> +	const __u64 permitted;

Why not "allowed" like the rule's field? Same for the variant names.

> +	const mode_t open_mode;
> +	/*
> +	 * These are the expected IOCTL results for a representative IOCTL from
> +	 * each of the IOCTL groups.  We only distinguish the 0 and EACCES
> +	 * results here, and treat other errors as 0.

In this case, why not use a boolean instead of a semi-correct error
code?

> +	 */
> +	const int expected_fioqsize_result; /* G1 */
> +	const int expected_fibmap_result; /* G2 */
> +	const int expected_fionread_result; /* G3 */
> +	const int expected_fs_ioc_zero_range_result; /* G4 */
> +	const int expected_fs_ioc_getflags_result; /* other */
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_none) {

You can remove all the variant's "ioctl_" prefixes.

> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_EXECUTE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,

You could use 0 instead and don't add the related rule in this case.

> +	.open_mode = O_RDWR,
> +	.expected_fioqsize_result = EACCES,
> +	.expected_fibmap_result = EACCES,
> +	.expected_fionread_result = EACCES,
> +	.expected_fs_ioc_zero_range_result = EACCES,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_i) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_IOCTL,
> +	.open_mode = O_RDWR,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = 0,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_unhandled) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_EXECUTE,
> +	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,
> +	.open_mode = O_RDWR,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = 0,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwd_permitted_r) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_READ_DIR,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
> +	.open_mode = O_RDONLY,
> +	/* If LANDLOCK_ACCESS_FS_IOCTL is not handled, all IOCTLs work. */
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = 0,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwd_permitted_w) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_READ_DIR,
> +	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
> +	.open_mode = O_WRONLY,
> +	/* If LANDLOCK_ACCESS_FS_IOCTL is not handled, all IOCTLs work. */
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = 0,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_ri_permitted_r) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
> +	.open_mode = O_RDONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = EACCES,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_wi_permitted_w) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
> +	.open_mode = O_WRONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = EACCES,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_di_permitted_d) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_DIR | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_DIR,
> +	.open_mode = O_RDWR,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = EACCES,
> +	.expected_fionread_result = EACCES,
> +	.expected_fs_ioc_zero_range_result = EACCES,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_rw) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_FILE |
> +		     LANDLOCK_ACCESS_FS_WRITE_FILE,
> +	.open_mode = O_RDWR,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_r) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_FILE,
> +	.open_mode = O_RDONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = EACCES,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_ri) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.open_mode = O_RDONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = 0,
> +	.expected_fs_ioc_zero_range_result = EACCES,
> +	.expected_fs_ioc_getflags_result = 0,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_w) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE,
> +	.open_mode = O_WRONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = EACCES,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = EACCES,
> +};
> +
> +/* clang-format off */
> +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_rwi_permitted_wi) {
> +	/* clang-format on */
> +	.handled = LANDLOCK_ACCESS_FS_READ_FILE |
> +		   LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.permitted = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_IOCTL,
> +	.open_mode = O_WRONLY,
> +	.expected_fioqsize_result = 0,
> +	.expected_fibmap_result = 0,
> +	.expected_fionread_result = EACCES,
> +	.expected_fs_ioc_zero_range_result = 0,
> +	.expected_fs_ioc_getflags_result = 0,
> +};

Great tests!

> +
> +static int test_fioqsize_ioctl(int fd)
> +{
> +	size_t sz;
> +
> +	if (ioctl(fd, FIOQSIZE, &sz) < 0)
> +		return errno;
> +	return 0;
> +}
> +
> +static int test_fibmap_ioctl(int fd)
> +{
> +	int blk = 0;
> +
> +	/*
> +	 * We only want to distinguish here whether Landlock already caught it,
> +	 * so we treat anything but EACCESS as success.  (It commonly returns
> +	 * EPERM when missing CAP_SYS_RAWIO.)
> +	 */
> +	if (ioctl(fd, FIBMAP, &blk) < 0 && errno == EACCES)
> +		return errno;
> +	return 0;
> +}
> +
> +static int test_fionread_ioctl(int fd)
> +{
> +	size_t sz = 0;
> +
> +	if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
> +		return errno;
> +	return 0;
> +}
> +
> +#define FS_IOC_ZERO_RANGE _IOW('X', 57, struct space_resv)
> +
> +static int test_fs_ioc_zero_range_ioctl(int fd)
> +{
> +	struct space_resv {
> +		__s16 l_type;
> +		__s16 l_whence;
> +		__s64 l_start;
> +		__s64 l_len; /* len == 0 means until end of file */
> +		__s32 l_sysid;
> +		__u32 l_pid;
> +		__s32 l_pad[4]; /* reserved area */
> +	} reservation = {};
> +	/*
> +	 * This can fail for various reasons, but we only want to distinguish
> +	 * here whether Landlock already caught it, so we treat anything but
> +	 * EACCES as success.
> +	 */
> +	if (ioctl(fd, FS_IOC_ZERO_RANGE, &reservation) < 0 && errno == EACCES)

What are the guarantees that an error different than EACCES would not
mask EACCES and then make tests pass whereas they should not?

> +		return errno;
> +	return 0;
> +}
> +
> +TEST_F_FORK(ioctl, handle_dir_access_file)
> +{
> +	const int flag = 0;
> +	const struct rule rules[] = {
> +		{
> +			.path = dir_s1d1,
> +			.access = variant->permitted,
> +		},
> +		{},
> +	};
> +	int fd, ruleset_fd;

Please rename fd into something like file_fd.

> +
> +	/* Enables Landlock. */
> +	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
> +	ASSERT_LE(0, ruleset_fd);
> +	enforce_ruleset(_metadata, ruleset_fd);
> +	ASSERT_EQ(0, close(ruleset_fd));
> +
> +	fd = open(file1_s1d1, variant->open_mode);
> +	ASSERT_LE(0, fd);
> +
> +	/*
> +	 * Checks that IOCTL commands in each IOCTL group return the expected
> +	 * errors.
> +	 */
> +	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
> +		  test_fs_ioc_zero_range_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
> +		  test_fs_ioc_getflags_ioctl(fd));
> +
> +	/* Checks that unrestrictable commands are unrestricted. */
> +	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
> +	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
> +
> +	ASSERT_EQ(0, close(fd));
> +}
> +
> +TEST_F_FORK(ioctl, handle_dir_access_dir)
> +{
> +	const char *const path = dir_s1d1;
> +	const int flag = 0;
> +	const struct rule rules[] = {
> +		{
> +			.path = path,
> +			.access = variant->permitted,
> +		},
> +		{},
> +	};
> +	int fd, ruleset_fd;
> +
> +	/* Enables Landlock. */
> +	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
> +	ASSERT_LE(0, ruleset_fd);
> +	enforce_ruleset(_metadata, ruleset_fd);
> +	ASSERT_EQ(0, close(ruleset_fd));
> +
> +	/*
> +	 * Ignore variant->open_mode for this test, as we intend to open a
> +	 * directory.  If the directory can not be opened, the variant is
> +	 * infeasible to test with an opened directory.
> +	 */
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0)
> +		return;
> +
> +	/*
> +	 * Checks that IOCTL commands in each IOCTL group return the expected
> +	 * errors.
> +	 */
> +	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
> +		  test_fs_ioc_zero_range_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
> +		  test_fs_ioc_getflags_ioctl(fd));
> +
> +	/* Checks that unrestrictable commands are unrestricted. */
> +	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
> +	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
> +
> +	ASSERT_EQ(0, close(fd));
> +}
> +
> +TEST_F_FORK(ioctl, handle_file_access_file)
> +{
> +	const char *const path = file1_s1d1;
> +	const int flag = 0;
> +	const struct rule rules[] = {
> +		{
> +			.path = path,
> +			.access = variant->permitted,
> +		},
> +		{},
> +	};
> +	int fd, ruleset_fd;
> +
> +	if (variant->permitted & LANDLOCK_ACCESS_FS_READ_DIR) {
> +		/* This access right can not be granted on files. */
> +		return;
> +	}

You should use SKIP().

> +
> +	/* Enables Landlock. */
> +	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
> +	ASSERT_LE(0, ruleset_fd);
> +	enforce_ruleset(_metadata, ruleset_fd);
> +	ASSERT_EQ(0, close(ruleset_fd));
> +
> +	fd = open(path, variant->open_mode);
> +	ASSERT_LE(0, fd);
> +
> +	/*
> +	 * Checks that IOCTL commands in each IOCTL group return the expected
> +	 * errors.
> +	 */
> +	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
> +		  test_fs_ioc_zero_range_ioctl(fd));
> +	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
> +		  test_fs_ioc_getflags_ioctl(fd));
> +
> +	/* Checks that unrestrictable commands are unrestricted. */
> +	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
> +	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
> +	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
> +
> +	ASSERT_EQ(0, close(fd));
> +}

Don't you want to create and use a common helper with most of these
TEST_F_FORK blocks? It would highlight what is the same or different,
and it would also enables to extend the coverage to other file types
(e.g. character device).

> +
>  /* clang-format off */
>  FIXTURE(layout1_bind) {};
>  /* clang-format on */
> -- 
> 2.43.0.rc1.413.gea7ed67945-goog
> 

Re: [PATCH v5 2/7] landlock: Add IOCTL access right

[Günther Noack]

Hello!

On Fri, Nov 17, 2023 at 09:45:47PM +0100, Mickaël Salaün wrote:
> On Fri, Nov 17, 2023 at 04:49:15PM +0100, Günther Noack wrote:
> > +static inline access_mask_t expand_ioctl(const access_mask_t handled,
> 
> Please remove all explicit inlines in the .c files, the compiler should
> be able to inline them if necessary, or it my not inline them at all
> anyway.  It would be nice to check the -O2 code to see what GCC or clang
> do though, and I guess they will inline this kind of pattern.

Done.


> > +					 const access_mask_t access,
> > +					 const access_mask_t src,
> > +					 const access_mask_t dst)
> > +{
> > +	if (!(handled & LANDLOCK_ACCESS_FS_IOCTL))
> > +		return 0;
> > +
> > +	access_mask_t copy_from = (handled & src) ? src :
> 
> Please declare variables at the beginning of blocks.

Done.


> > +static inline access_mask_t
> > +landlock_expand_access_fs(const access_mask_t handled,
> > +			  const access_mask_t access)
> > +{
> > +	return access |
> > +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_WRITE_FILE,
> > +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
> > +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
> > +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP4) |
> > +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_FILE,
> > +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1 |
> > +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP2 |
> > +				    LANDLOCK_ACCESS_FS_IOCTL_GROUP3) |
> > +	       expand_ioctl(handled, access, LANDLOCK_ACCESS_FS_READ_DIR,
> > +			    LANDLOCK_ACCESS_FS_IOCTL_GROUP1);
> > +}
> 
> I'd prefer to keep the semantic definition of these groups (i.e.
> required_ioctl_access) close the definition of access right expantions,
> and also close to the ioctl_groups veriable. Actually, ioctl_groups
> might make more sense close to the group definition, and then probably
> another define... What do you think?

Done, good idea. Thanks for the suggestion!

I think this makes sense and the code looks better when the IOCTL-related
functionality is grouped together at the top of fs.c, including ioctl_groups,
the LANDLOCK_ACCESS_FS_IOCTL_GROUP1,2,3,4 #defines, the expansion helpers and
the required_ioctl_access helper.


> > +	/*
> > +	 * It is the access rights at the time of opening the file which
> > +	 * determine whether ioctl can be used on the opened file later.
> 
> s/ioctl/IOCTL/g

Done.


> > +/**
> > + * landlock_expand_handled_access_fs() - add synthetic IOCTL access rights to an
> > + * access mask of handled accesses.
> > + *
> > + * @handled: The handled accesses of a ruleset that is being created
> > + *
> > + * Returns: @handled, with the bits for the synthetic IOCTL access rights set,
> > + * if %LANDLOCK_ACCESS_FS_IOCTL is handled
> > + */
> 
> This doc should be in fs.c

Done, thanks.

(I did not realize that the convention worked this way in the kernel.  This goes
on my bucket list of things to double check.)

Thanks for the review!

—Günther

Re: [PATCH v5 2/7] landlock: Add IOCTL access right

[Günther Noack]

On Mon, Nov 20, 2023 at 08:43:30PM +0100, Mickaël Salaün wrote:
> On Fri, Nov 17, 2023 at 04:49:15PM +0100, Günther Noack wrote:
> > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP1	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1)
> > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP2	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 2)
> > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP3	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 3)
> > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP4	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 4)
> 
> Please move this LANDLOCK_ACCESS_FS_IOCTL_* block to fs.h
> 
> We can still create the public and private masks in limits.h but add a
> static_assert() to make sure there is no overlap.

Done.


> >  	/* Checks content (and 32-bits cast). */
> > -	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
> > -	    LANDLOCK_MASK_ACCESS_FS)
> > +	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_PUBLIC_ACCESS_FS) !=
> > +	    LANDLOCK_MASK_PUBLIC_ACCESS_FS)
> 
> It would now be possible to add LANDLOCK_ACCESS_FS_IOCTL_GROUP* to a
> rule, which is not part of the API/ABI. I've sent a patch with new tests
> to make sure this is covered:
> https://lore.kernel.org/r/20231120193914.441117-2-mic@digikod.net
> 
> I'll push it in my -next branch if everything is OK before pushing your
> next series. Please review it.

Thanks, good catch!

Looking at add_rule_path_beneath(), it indeed does not look like I have covered
that case in my patch.  I'll put an explicit check for it, like this:

  /*
   * Checks that allowed_access matches the @ruleset constraints and only
   * consists of publicly visible access rights (as opposed to synthetic
   * ones).
   */
  mask = landlock_get_raw_fs_access_mask(ruleset, 0) &
         LANDLOCK_MASK_PUBLIC_ACCESS_FS;
  if ((path_beneath_attr.allowed_access | mask) != mask)
          return -EINVAL;

I assume that the tests that you added were failing?  Or was there an obscure
code path that caught it anyway?

Thanks,
—Günther

Re: [PATCH v5 3/7] selftests/landlock: Test IOCTL support

[Günther Noack]

Hi!

On Mon, Nov 20, 2023 at 09:41:20PM +0100, Mickaël Salaün wrote:
> On Fri, Nov 17, 2023 at 04:49:16PM +0100, Günther Noack wrote:
> > +FIXTURE_VARIANT(ioctl)
> > +{
> > +	const __u64 handled;
> > +	const __u64 permitted;
> 
> Why not "allowed" like the rule's field? Same for the variant names.

Just for consistency with the ftruncate tests which also named it like that... %-)

Sounds good though, I'll just rename it in both places.


> > +	const mode_t open_mode;
> > +	/*
> > +	 * These are the expected IOCTL results for a representative IOCTL from
> > +	 * each of the IOCTL groups.  We only distinguish the 0 and EACCES
> > +	 * results here, and treat other errors as 0.
> 
> In this case, why not use a boolean instead of a semi-correct error
> code?

I found it slightly less convoluted.  When we use booleans here, we need to map
between error codes and booleans at a different layer.  At the same time, we
already have various test_foo_ioctl() and test_foo() functions, and they are
sometimes also used in other contexts like test_fs_ioc_getflags_ioctl().  These
test_foo() helpers generally return error codes so far, and it felt more
important to stay consistent with that.  If we want to keep that both, the only
other place to map between booleans and error codes would be with ternary
operators or such in the EXPECT_EQ clauses, but that also felt like it would
turn unreadable... %-)

I can change it if you feel strongly about it though. Let me know.

> > +	 */
> > +	const int expected_fioqsize_result; /* G1 */
> > +	const int expected_fibmap_result; /* G2 */
> > +	const int expected_fionread_result; /* G3 */
> > +	const int expected_fs_ioc_zero_range_result; /* G4 */
> > +	const int expected_fs_ioc_getflags_result; /* other */
> > +};
> > +
> > +/* clang-format off */
> > +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_none) {
> 
> You can remove all the variant's "ioctl_" prefixes.

Done.


> > +	/* clang-format on */
> > +	.handled = LANDLOCK_ACCESS_FS_EXECUTE | LANDLOCK_ACCESS_FS_IOCTL,
> > +	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,
> 
> You could use 0 instead and don't add the related rule in this case.

Done.


> Great tests!

Thanks :)


> > +static int test_fioqsize_ioctl(int fd)
> > +{
> > +	size_t sz;
> > +
> > +	if (ioctl(fd, FIOQSIZE, &sz) < 0)
> > +		return errno;
> > +	return 0;
> > +}
> > +
> > +static int test_fibmap_ioctl(int fd)
> > +{
> > +	int blk = 0;
> > +
> > +	/*
> > +	 * We only want to distinguish here whether Landlock already caught it,
> > +	 * so we treat anything but EACCESS as success.  (It commonly returns
> > +	 * EPERM when missing CAP_SYS_RAWIO.)
> > +	 */
> > +	if (ioctl(fd, FIBMAP, &blk) < 0 && errno == EACCES)
> > +		return errno;
> > +	return 0;
> > +}
> > +
> > +static int test_fionread_ioctl(int fd)
> > +{
> > +	size_t sz = 0;
> > +
> > +	if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
> > +		return errno;
> > +	return 0;
> > +}
> > +
> > +#define FS_IOC_ZERO_RANGE _IOW('X', 57, struct space_resv)
> > +
> > +static int test_fs_ioc_zero_range_ioctl(int fd)
> > +{
> > +	struct space_resv {
> > +		__s16 l_type;
> > +		__s16 l_whence;
> > +		__s64 l_start;
> > +		__s64 l_len; /* len == 0 means until end of file */
> > +		__s32 l_sysid;
> > +		__u32 l_pid;
> > +		__s32 l_pad[4]; /* reserved area */
> > +	} reservation = {};
> > +	/*
> > +	 * This can fail for various reasons, but we only want to distinguish
> > +	 * here whether Landlock already caught it, so we treat anything but
> > +	 * EACCES as success.
> > +	 */
> > +	if (ioctl(fd, FS_IOC_ZERO_RANGE, &reservation) < 0 && errno == EACCES)
> 
> What are the guarantees that an error different than EACCES would not
> mask EACCES and then make tests pass whereas they should not?

It is indeed possible that one of these ioctls legitimately returns EACCES after
Landlock was letting that ioctl through, and then we could not tell apart
whether Landlock blocked it or whether the underlying IOCTL command returned
that.  I double checked that this is not the case for these specific
invocations.  But with some other IOCTL commands in these groups, I believe I
was getting EACCES sometimes from the IOCTL.  So we only use one representative
IOCTL from each IOCTL group, for which it happened to work.

To convince yourself, you can see in the tests that we have both "success" and
"blocked" examples in the tests for each of these IOCTL commands, and the
Landlock rules are the only difference between these examples. Therefore, we
know that it is actually Landlock returning the EACCES and not the underlying
IOCTL.

> > +		return errno;
> > +	return 0;
> > +}
> > +
> > +TEST_F_FORK(ioctl, handle_dir_access_file)
> > +{
> > +	const int flag = 0;
> > +	const struct rule rules[] = {
> > +		{
> > +			.path = dir_s1d1,
> > +			.access = variant->permitted,
> > +		},
> > +		{},
> > +	};
> > +	int fd, ruleset_fd;
> 
> Please rename fd into something like file_fd.

Done.


> > +TEST_F_FORK(ioctl, handle_file_access_file)
> > +{
> > +	const char *const path = file1_s1d1;
> > +	const int flag = 0;
> > +	const struct rule rules[] = {
> > +		{
> > +			.path = path,
> > +			.access = variant->permitted,
> > +		},
> > +		{},
> > +	};
> > +	int fd, ruleset_fd;
> > +
> > +	if (variant->permitted & LANDLOCK_ACCESS_FS_READ_DIR) {
> > +		/* This access right can not be granted on files. */
> > +		return;
> > +	}
> 
> You should use SKIP().

Done.


> > +	/* Enables Landlock. */
> > +	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
> > +	ASSERT_LE(0, ruleset_fd);
> > +	enforce_ruleset(_metadata, ruleset_fd);
> > +	ASSERT_EQ(0, close(ruleset_fd));
> > +
> > +	fd = open(path, variant->open_mode);
> > +	ASSERT_LE(0, fd);
> > +
> > +	/*
> > +	 * Checks that IOCTL commands in each IOCTL group return the expected
> > +	 * errors.
> > +	 */
> > +	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
> > +	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
> > +	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
> > +	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
> > +		  test_fs_ioc_zero_range_ioctl(fd));
> > +	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
> > +		  test_fs_ioc_getflags_ioctl(fd));
> > +
> > +	/* Checks that unrestrictable commands are unrestricted. */
> > +	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
> > +	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
> > +	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
> > +	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
> > +
> > +	ASSERT_EQ(0, close(fd));
> > +}
> 
> Don't you want to create and use a common helper with most of these
> TEST_F_FORK blocks? It would highlight what is the same or different,
> and it would also enables to extend the coverage to other file types
> (e.g. character device).

I did not find a good way to factor this out, to be honest, and so preferred to
keep it unrolled.

I try to follow the rule of not putting too many "if" conditions and logic into
my tests (it helps to keep the tests straightforward and understandable), and I
find it more straightforward to spell out these few EXPECT_EQs three times than
introducing a "test_all_ioctl_expectations()" helper function :)

—Günther

Re: [PATCH v5 2/7] landlock: Add IOCTL access right

[Mickaël Salaün]

On Fri, Nov 24, 2023 at 04:39:02PM +0100, Günther Noack wrote:
> On Mon, Nov 20, 2023 at 08:43:30PM +0100, Mickaël Salaün wrote:
> > On Fri, Nov 17, 2023 at 04:49:15PM +0100, Günther Noack wrote:
> > > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP1	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 1)
> > > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP2	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 2)
> > > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP3	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 3)
> > > +#define LANDLOCK_ACCESS_FS_IOCTL_GROUP4	(LANDLOCK_LAST_PUBLIC_ACCESS_FS << 4)
> > 
> > Please move this LANDLOCK_ACCESS_FS_IOCTL_* block to fs.h
> > 
> > We can still create the public and private masks in limits.h but add a
> > static_assert() to make sure there is no overlap.
> 
> Done.
> 
> 
> > >  	/* Checks content (and 32-bits cast). */
> > > -	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
> > > -	    LANDLOCK_MASK_ACCESS_FS)
> > > +	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_PUBLIC_ACCESS_FS) !=
> > > +	    LANDLOCK_MASK_PUBLIC_ACCESS_FS)
> > 
> > It would now be possible to add LANDLOCK_ACCESS_FS_IOCTL_GROUP* to a
> > rule, which is not part of the API/ABI. I've sent a patch with new tests
> > to make sure this is covered:
> > https://lore.kernel.org/r/20231120193914.441117-2-mic@digikod.net
> > 
> > I'll push it in my -next branch if everything is OK before pushing your
> > next series. Please review it.
> 
> Thanks, good catch!
> 
> Looking at add_rule_path_beneath(), it indeed does not look like I have covered
> that case in my patch.  I'll put an explicit check for it, like this:
> 
>   /*
>    * Checks that allowed_access matches the @ruleset constraints and only
>    * consists of publicly visible access rights (as opposed to synthetic
>    * ones).
>    */
>   mask = landlock_get_raw_fs_access_mask(ruleset, 0) &
>          LANDLOCK_MASK_PUBLIC_ACCESS_FS;
>   if ((path_beneath_attr.allowed_access | mask) != mask)
>           return -EINVAL;
> 
> I assume that the tests that you added were failing?  Or was there an obscure
> code path that caught it anyway?

Yep, it was failing, but it works with the v6.

> 
> Thanks,
> —Günther
> 

Re: [PATCH v5 3/7] selftests/landlock: Test IOCTL support

[Mickaël Salaün]

On Fri, Nov 24, 2023 at 05:57:31PM +0100, Günther Noack wrote:
> Hi!
> 
> On Mon, Nov 20, 2023 at 09:41:20PM +0100, Mickaël Salaün wrote:
> > On Fri, Nov 17, 2023 at 04:49:16PM +0100, Günther Noack wrote:
> > > +FIXTURE_VARIANT(ioctl)
> > > +{
> > > +	const __u64 handled;
> > > +	const __u64 permitted;
> > 
> > Why not "allowed" like the rule's field? Same for the variant names.
> 
> Just for consistency with the ftruncate tests which also named it like that... %-)
> 
> Sounds good though, I'll just rename it in both places.
> 
> 
> > > +	const mode_t open_mode;
> > > +	/*
> > > +	 * These are the expected IOCTL results for a representative IOCTL from
> > > +	 * each of the IOCTL groups.  We only distinguish the 0 and EACCES
> > > +	 * results here, and treat other errors as 0.
> > 
> > In this case, why not use a boolean instead of a semi-correct error
> > code?
> 
> I found it slightly less convoluted.  When we use booleans here, we need to map
> between error codes and booleans at a different layer.  At the same time, we
> already have various test_foo_ioctl() and test_foo() functions, and they are
> sometimes also used in other contexts like test_fs_ioc_getflags_ioctl().  These
> test_foo() helpers generally return error codes so far, and it felt more
> important to stay consistent with that.  If we want to keep that both, the only
> other place to map between booleans and error codes would be with ternary
> operators or such in the EXPECT_EQ clauses, but that also felt like it would
> turn unreadable... %-)

Sounds good.

> 
> I can change it if you feel strongly about it though. Let me know.
> 
> > > +	 */
> > > +	const int expected_fioqsize_result; /* G1 */
> > > +	const int expected_fibmap_result; /* G2 */
> > > +	const int expected_fionread_result; /* G3 */
> > > +	const int expected_fs_ioc_zero_range_result; /* G4 */
> > > +	const int expected_fs_ioc_getflags_result; /* other */
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(ioctl, ioctl_handled_i_permitted_none) {
> > 
> > You can remove all the variant's "ioctl_" prefixes.
> 
> Done.
> 
> 
> > > +	/* clang-format on */
> > > +	.handled = LANDLOCK_ACCESS_FS_EXECUTE | LANDLOCK_ACCESS_FS_IOCTL,
> > > +	.permitted = LANDLOCK_ACCESS_FS_EXECUTE,
> > 
> > You could use 0 instead and don't add the related rule in this case.
> 
> Done.
> 
> 
> > Great tests!
> 
> Thanks :)
> 
> 
> > > +static int test_fioqsize_ioctl(int fd)
> > > +{
> > > +	size_t sz;
> > > +
> > > +	if (ioctl(fd, FIOQSIZE, &sz) < 0)
> > > +		return errno;
> > > +	return 0;
> > > +}
> > > +
> > > +static int test_fibmap_ioctl(int fd)
> > > +{
> > > +	int blk = 0;
> > > +
> > > +	/*
> > > +	 * We only want to distinguish here whether Landlock already caught it,
> > > +	 * so we treat anything but EACCESS as success.  (It commonly returns
> > > +	 * EPERM when missing CAP_SYS_RAWIO.)
> > > +	 */
> > > +	if (ioctl(fd, FIBMAP, &blk) < 0 && errno == EACCES)
> > > +		return errno;
> > > +	return 0;
> > > +}
> > > +
> > > +static int test_fionread_ioctl(int fd)
> > > +{
> > > +	size_t sz = 0;
> > > +
> > > +	if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
> > > +		return errno;
> > > +	return 0;
> > > +}
> > > +
> > > +#define FS_IOC_ZERO_RANGE _IOW('X', 57, struct space_resv)
> > > +
> > > +static int test_fs_ioc_zero_range_ioctl(int fd)
> > > +{
> > > +	struct space_resv {
> > > +		__s16 l_type;
> > > +		__s16 l_whence;
> > > +		__s64 l_start;
> > > +		__s64 l_len; /* len == 0 means until end of file */
> > > +		__s32 l_sysid;
> > > +		__u32 l_pid;
> > > +		__s32 l_pad[4]; /* reserved area */
> > > +	} reservation = {};
> > > +	/*
> > > +	 * This can fail for various reasons, but we only want to distinguish
> > > +	 * here whether Landlock already caught it, so we treat anything but
> > > +	 * EACCES as success.
> > > +	 */
> > > +	if (ioctl(fd, FS_IOC_ZERO_RANGE, &reservation) < 0 && errno == EACCES)
> > 
> > What are the guarantees that an error different than EACCES would not
> > mask EACCES and then make tests pass whereas they should not?
> 
> It is indeed possible that one of these ioctls legitimately returns EACCES after
> Landlock was letting that ioctl through, and then we could not tell apart
> whether Landlock blocked it or whether the underlying IOCTL command returned
> that.  I double checked that this is not the case for these specific
> invocations.  But with some other IOCTL commands in these groups, I believe I
> was getting EACCES sometimes from the IOCTL.  So we only use one representative
> IOCTL from each IOCTL group, for which it happened to work.
> 
> To convince yourself, you can see in the tests that we have both "success" and
> "blocked" examples in the tests for each of these IOCTL commands, and the
> Landlock rules are the only difference between these examples. Therefore, we
> know that it is actually Landlock returning the EACCES and not the underlying
> IOCTL.

This is correct, at least for now. Let's stick to that.

> 
> > > +		return errno;
> > > +	return 0;
> > > +}
> > > +
> > > +TEST_F_FORK(ioctl, handle_dir_access_file)
> > > +{
> > > +	const int flag = 0;
> > > +	const struct rule rules[] = {
> > > +		{
> > > +			.path = dir_s1d1,
> > > +			.access = variant->permitted,
> > > +		},
> > > +		{},
> > > +	};
> > > +	int fd, ruleset_fd;
> > 
> > Please rename fd into something like file_fd.
> 
> Done.
> 
> 
> > > +TEST_F_FORK(ioctl, handle_file_access_file)
> > > +{
> > > +	const char *const path = file1_s1d1;
> > > +	const int flag = 0;
> > > +	const struct rule rules[] = {
> > > +		{
> > > +			.path = path,
> > > +			.access = variant->permitted,
> > > +		},
> > > +		{},
> > > +	};
> > > +	int fd, ruleset_fd;
> > > +
> > > +	if (variant->permitted & LANDLOCK_ACCESS_FS_READ_DIR) {
> > > +		/* This access right can not be granted on files. */
> > > +		return;
> > > +	}
> > 
> > You should use SKIP().
> 
> Done.
> 
> 
> > > +	/* Enables Landlock. */
> > > +	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
> > > +	ASSERT_LE(0, ruleset_fd);
> > > +	enforce_ruleset(_metadata, ruleset_fd);
> > > +	ASSERT_EQ(0, close(ruleset_fd));
> > > +
> > > +	fd = open(path, variant->open_mode);
> > > +	ASSERT_LE(0, fd);
> > > +
> > > +	/*
> > > +	 * Checks that IOCTL commands in each IOCTL group return the expected
> > > +	 * errors.
> > > +	 */
> > > +	EXPECT_EQ(variant->expected_fioqsize_result, test_fioqsize_ioctl(fd));
> > > +	EXPECT_EQ(variant->expected_fibmap_result, test_fibmap_ioctl(fd));
> > > +	EXPECT_EQ(variant->expected_fionread_result, test_fionread_ioctl(fd));
> > > +	EXPECT_EQ(variant->expected_fs_ioc_zero_range_result,
> > > +		  test_fs_ioc_zero_range_ioctl(fd));
> > > +	EXPECT_EQ(variant->expected_fs_ioc_getflags_result,
> > > +		  test_fs_ioc_getflags_ioctl(fd));
> > > +
> > > +	/* Checks that unrestrictable commands are unrestricted. */
> > > +	EXPECT_EQ(0, ioctl(fd, FIOCLEX));
> > > +	EXPECT_EQ(0, ioctl(fd, FIONCLEX));
> > > +	EXPECT_EQ(0, ioctl(fd, FIONBIO, &flag));
> > > +	EXPECT_EQ(0, ioctl(fd, FIOASYNC, &flag));
> > > +
> > > +	ASSERT_EQ(0, close(fd));
> > > +}
> > 
> > Don't you want to create and use a common helper with most of these
> > TEST_F_FORK blocks? It would highlight what is the same or different,
> > and it would also enables to extend the coverage to other file types
> > (e.g. character device).
> 
> I did not find a good way to factor this out, to be honest, and so preferred to
> keep it unrolled.
> 
> I try to follow the rule of not putting too many "if" conditions and logic into
> my tests (it helps to keep the tests straightforward and understandable), and I
> find it more straightforward to spell out these few EXPECT_EQs three times than
> introducing a "test_all_ioctl_expectations()" helper function :)

I understand, but I'm not sure there would be so much "if" that it would
be difficult to understand. Did you try to factor it out with the
_metadata argument?

> 
> —Günther
>