kernel.git/security/landlock/fs.c, branch linux-rolling-lts

landlock: Fix handling of disconnected directories

2025-12-18T13:03:27Z

[ Upstream commit 49c9e09d961025b22e61ef9ad56aa1c21b6ce2f1 ] Disconnected files or directories can appear when they are visible and opened from a bind mount, but have been renamed or moved from the source of the bind mount in a way that makes them inaccessible from the mount point (i.e. out of scope). Previously, access rights tied to files or directories opened through a disconnected directory were collected by walking the related hierarchy down to the root of the filesystem, without taking into account the mount point because it couldn't be found. This could lead to inconsistent access results, potential access right widening, and hard-to-debug renames, especially since such paths cannot be printed. For a sandboxed task to create a disconnected directory, it needs to have write access (i.e. FS_MAKE_REG, FS_REMOVE_FILE, and FS_REFER) to the underlying source of the bind mount, and read access to the related mount point. Because a sandboxed task cannot acquire more access rights than those defined by its Landlock domain, this could lead to inconsistent access rights due to missing permissions that should be inherited from the mount point hierarchy, while inheriting permissions from the filesystem hierarchy hidden by this mount point instead. Landlock now handles files and directories opened from disconnected directories by taking into account the filesystem hierarchy when the mount point is not found in the hierarchy walk, and also always taking into account the mount point from which these disconnected directories were opened. This ensures that a rename is not allowed if it would widen access rights [1]. The rationale is that, even if disconnected hierarchies might not be visible or accessible to a sandboxed task, relying on the collected access rights from them improves the guarantee that access rights will not be widened during a rename because of the access right comparison between the source and the destination (see LANDLOCK_ACCESS_FS_REFER). It may look like this would grant more access on disconnected files and directories, but the security policies are always enforced for all the evaluated hierarchies. This new behavior should be less surprising to users and safer from an access control perspective. Remove a wrong WARN_ON_ONCE() canary in collect_domain_accesses() and fix the related comment. Because opened files have their access rights stored in the related file security properties, there is no impact for disconnected or unlinked files. Cc: Christian Brauner Cc: Günther Noack Cc: Song Liu Reported-by: Tingmao Wang Closes: https://lore.kernel.org/r/027d5190-b37a-40a8-84e9-4ccbc352bcdf@maowtm.org Closes: https://lore.kernel.org/r/09b24128f86973a6022e6aa8338945fcfb9a33e4.1749925391.git.m@maowtm.org Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER") Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control") Link: https://lore.kernel.org/r/b0f46246-f2c5-42ca-93ce-0d629702a987@maowtm.org [1] Reviewed-by: Tingmao Wang Link: https://lore.kernel.org/r/20251128172200.760753-2-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Sasha Levin

landlock: fix splats from iput() after it started calling might_sleep()

2025-11-12T09:47:42Z

At this point it is guaranteed this is not the last reference. However, a recent addition of might_sleep() at top of iput() started generating false-positives as it was executing for all values. Remedy the problem by using the newly introduced iput_not_last(). Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68d32659.a70a0220.4f78.0012.GAE@google.com/ Fixes: 2ef435a872ab ("fs: add might_sleep() annotation to iput() and more") Signed-off-by: Mateusz Guzik Link: https://patch.msgid.link/20251105212025.807549-2-mjguzik@gmail.com Reviewed-by: Mickaël Salaün Signed-off-by: Christian Brauner

fs: add an icount_read helper

2025-09-01T10:41:09Z

Instead of doing direct access to ->i_count, add a helper to handle this. This will make it easier to convert i_count to a refcount later. Signed-off-by: Josef Bacik Link: https://lore.kernel.org/9bc62a84c6b9d6337781203f60837bd98fbc4a96.1756222464.git.josef@toxicpanda.com Signed-off-by: Christian Brauner

landlock: Fix cosmetic change

2025-07-19T10:44:16Z

This line removal should not be there and it makes it more difficult to backport the following patch. Cc: Günther Noack Cc: Konstantin Meskhidze Fixes: 7a11275c3787 ("landlock: Refactor layer helpers") Link: https://lore.kernel.org/r/20250719104204.545188-2-mic@digikod.net Signed-off-by: Mickaël Salaün

Merge tag 'landlock-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

2025-03-28T19:37:13Z

Pull landlock updates from Mickaël Salaün: "This brings two main changes to Landlock: - A signal scoping fix with a new interface for user space to know if it is compatible with the running kernel. - Audit support to give visibility on why access requests are denied, including the origin of the security policy, missing access rights, and description of object(s). This was designed to limit log spam as much as possible while still alerting about unexpected blocked access. With these changes come new and improved documentation, and a lot of new tests" * tag 'landlock-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: (36 commits) landlock: Add audit documentation selftests/landlock: Add audit tests for network selftests/landlock: Add audit tests for filesystem selftests/landlock: Add audit tests for abstract UNIX socket scoping selftests/landlock: Add audit tests for ptrace selftests/landlock: Test audit with restrict flags selftests/landlock: Add tests for audit flags and domain IDs selftests/landlock: Extend tests for landlock_restrict_self(2)'s flags selftests/landlock: Add test for invalid ruleset file descriptor samples/landlock: Enable users to log sandbox denials landlock: Add LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF landlock: Add LANDLOCK_RESTRICT_SELF_LOG_*_EXEC_* flags landlock: Log scoped denials landlock: Log TCP bind and connect denials landlock: Log truncate and IOCTL denials landlock: Factor out IOCTL hooks landlock: Log file-related denials landlock: Log mount-related denials landlock: Add AUDIT_LANDLOCK_DOMAIN and log domain status landlock: Add AUDIT_LANDLOCK_ACCESS and log ptrace denials ...

landlock: Log scoped denials

2025-03-26T12:59:42Z

Add audit support for unix_stream_connect, unix_may_send, task_kill, and file_send_sigiotask hooks. The related blockers are: - scope.abstract_unix_socket - scope.signal Audit event sample for abstract unix socket: type=LANDLOCK_DENY msg=audit(1729738800.268:30): domain=195ba459b blockers=scope.abstract_unix_socket path=00666F6F Audit event sample for signal: type=LANDLOCK_DENY msg=audit(1729738800.291:31): domain=195ba459b blockers=scope.signal opid=1 ocomm="systemd" Refactor and simplify error handling in LSM hooks. Extend struct landlock_file_security with fown_layer and use it to log the blocking domain. The struct aligned size is still 16 bytes. Cc: Günther Noack Cc: Tahera Fahimi Link: https://lore.kernel.org/r/20250320190717.2287696-17-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Log truncate and IOCTL denials

2025-03-26T12:59:41Z

Add audit support to the file_truncate and file_ioctl hooks. Add a deny_masks_t type and related helpers to store the domain's layer level per optional access rights (i.e. LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL_DEV) when opening a file, which cannot be inferred later. In practice, the landlock_file_security aligned blob size is still 16 bytes because this new one-byte deny_masks field follows the existing two-bytes allowed_access field and precede the packed fown_subject. Implementing deny_masks_t with a bitfield instead of a struct enables a generic implementation to store and extract layer levels. Add KUnit tests to check the identification of a layer level from a deny_masks_t, and the computation of a deny_masks_t from an access right with its layer level or a layer_mask_t array. Audit event sample: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.ioctl_dev path="/dev/tty" dev="devtmpfs" ino=9 ioctlcmd=0x5401 Cc: Günther Noack Link: https://lore.kernel.org/r/20250320190717.2287696-15-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Factor out IOCTL hooks

2025-03-26T12:59:40Z

Compat and non-compat IOCTL hooks are almost the same, except to compare the IOCTL command. Factor out these two IOCTL hooks to highlight the difference and minimize audit changes (see next commit). Cc: Günther Noack Link: https://lore.kernel.org/r/20250320190717.2287696-14-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Log file-related denials

2025-03-26T12:59:39Z

Add audit support for path_mkdir, path_mknod, path_symlink, path_unlink, path_rmdir, path_truncate, path_link, path_rename, and file_open hooks. The dedicated blockers are: - fs.execute - fs.write_file - fs.read_file - fs.read_dir - fs.remove_dir - fs.remove_file - fs.make_char - fs.make_dir - fs.make_reg - fs.make_sock - fs.make_fifo - fs.make_block - fs.make_sym - fs.refer - fs.truncate - fs.ioctl_dev Audit event sample for a denied link action: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.refer path="/usr/bin" dev="vda2" ino=351 type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.make_reg,fs.refer path="/usr/local" dev="vda2" ino=365 We could pack blocker names (e.g. "fs:make_reg,refer") but that would increase complexity for the kernel and log parsers. Moreover, this could not handle blockers of different classes (e.g. fs and net). Make it simple and flexible instead. Add KUnit tests to check the identification from a layer_mask_t array of the first layer level denying such request. Cc: Günther Noack Depends-on: 058518c20920 ("landlock: Align partial refer access checks with final ones") Depends-on: d617f0d72d80 ("landlock: Optimize file path walks and prepare for audit support") Link: https://lore.kernel.org/r/20250320190717.2287696-13-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Log mount-related denials

2025-03-26T12:59:39Z

Add audit support for sb_mount, move_mount, sb_umount, sb_remount, and sb_pivot_root hooks. The new related blocker is "fs.change_topology". Audit event sample: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.change_topology name="/" dev="tmpfs" ino=1 Remove landlock_get_applicable_domain() and get_current_fs_domain() which are now fully replaced with landlock_get_applicable_subject(). Cc: Günther Noack Link: https://lore.kernel.org/r/20250320190717.2287696-12-mic@digikod.net Signed-off-by: Mickaël Salaün