kernel/linux.git/security/landlock/audit.c, branch v7.0.10

landlock: Transpose the layer masks data structure

2026-02-10T15:46:50+00:00

The layer masks data structure tracks the requested but unfulfilled access rights during an operation's security check. It stores one bit for each combination of access right and layer index. If the bit is set, that access right is not granted (yet) in the given layer and we have to traverse the path further upwards to grant it. Previously, the layer masks were stored as arrays mapping from access right indices to layer_mask_t. The layer_mask_t value then indicates all layers in which the given access right is still (tentatively) denied. This patch introduces struct layer_access_masks instead: This struct contains an array with the access_mask_t of each (tentatively) denied access right in that layer. The hypothesis of this patch is that this simplifies the code enough so that the resulting code will run faster: * We can use bitwise operations in multiple places where we previously looped over bits individually with macros. (Should require less branch speculation and lends itself to better loop unrolling.) * Code is ~75 lines smaller. Other noteworthy changes: * In no_more_access(), call a new helper function may_refer(), which only solves the asymmetric case. Previously, the code interleaved the checks for the two symmetric cases in RENAME_EXCHANGE. It feels that the code is clearer when renames without RENAME_EXCHANGE are more obviously the normal case. Tradeoffs: This change improves performance, at a slight size increase to the layer masks data structure. This fixes the size of the data structure at 32 bytes for all types of access rights. (64, once we introduce a 17th filesystem access right). For filesystem access rights, at the moment, the data structure has the same size as before, but once we introduce the 17th filesystem access right, it will double in size (from 32 to 64 bytes), as access_mask_t grows from 16 to 32 bit [1]. Link: https://lore.kernel.org/all/20260120.haeCh4li9Vae@digikod.net/ [1] Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20260206151154.97915-5-gnoack3000@gmail.com [mic: Cosmetic fixes, moved struct layer_access_masks definition] Signed-off-by: Mickaël Salaün

landlock: Fix wrong type usage

2025-12-26T19:38:59+00:00

I think, based on my best understanding, that this type is likely a typo (even though in the end both are u16) Signed-off-by: Tingmao Wang Fixes: 2fc80c69df82 ("landlock: Log file-related denials") Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/7339ad7b47f998affd84ca629a334a71f913616d.1765040503.git.m@maowtm.org Signed-off-by: Mickaël Salaün

landlock: Improve bit operations in audit code

2025-05-12T09:38:53+00:00

Use the BIT() and BIT_ULL() macros in the new audit code instead of explicit shifts to improve readability. Use bitmask instead of modulo operation to simplify code. Add test_range1_rand15() and test_range2_rand15() KUnit tests to improve get_id_range() coverage. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20250512093732.1408485-1-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Remove KUnit test that triggers a warning

2025-05-03T06:55:42+00:00

A KUnit test checking boundaries triggers a canary warning, which may be disturbing. Let's remove this test for now. Hopefully, KUnit will soon get support for suppressing warning backtraces [1]. Cc: Alessandro Carminati Cc: Andrew Morton Cc: Günther Noack Reported-by: Tingmao Wang Closes: https://lore.kernel.org/r/20250327213807.12964-1-m@maowtm.org Link: https://lore.kernel.org/r/20250425193249.78b45d2589575c15f483c3d8@linux-foundation.org [1] Link: https://lore.kernel.org/r/20250503065359.3625407-1-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Add LANDLOCK_RESTRICT_SELF_LOG__EXEC_ flags

2025-03-26T12:59:42+00:00

Most of the time we want to log denied access because they should not happen and such information helps diagnose issues. However, when sandboxing processes that we know will try to access denied resources (e.g. unknown, bogus, or malicious binary), we might want to not log related access requests that might fill up logs. By default, denied requests are logged until the task call execve(2). If the LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF flag is set, denied requests will not be logged for the same executed file. If the LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON flag is set, denied requests from after an execve(2) call will be logged. The rationale is that a program should know its own behavior, but not necessarily the behavior of other programs. Because LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF is set for a specific Landlock domain, it makes it possible to selectively mask some access requests that would be logged by a parent domain, which might be handy for unprivileged processes to limit logs. However, system administrators should still use the audit filtering mechanism. There is intentionally no audit nor sysctl configuration to re-enable these logs. This is delegated to the user space program. Increment the Landlock ABI version to reflect this interface change. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250320190717.2287696-18-mic@digikod.net [mic: Rename variables and fix __maybe_unused] Signed-off-by: Mickaël Salaün

landlock: Log scoped denials

2025-03-26T12:59:42+00:00

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 TCP bind and connect denials

2025-03-26T12:59:41+00:00

Add audit support to socket_bind and socket_connect hooks. The related blockers are: - net.bind_tcp - net.connect_tcp Audit event sample: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=net.connect_tcp daddr=127.0.0.1 dest=80 Cc: Günther Noack Cc: Konstantin Meskhidze Cc: Mikhail Ivanov Link: https://lore.kernel.org/r/20250320190717.2287696-16-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Log truncate and IOCTL denials

2025-03-26T12:59:41+00:00

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: Log file-related denials

2025-03-26T12:59:39+00:00

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

2025-03-26T12:59:39+00:00

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

kernel/linux.git/security/landlock/audit.c, branch v7.0.10

landlock: Transpose the layer masks data structure

landlock: Fix wrong type usage

landlock: Improve bit operations in audit code

landlock: Remove KUnit test that triggers a warning

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: Log file-related denials

landlock: Log mount-related denials

landlock: Add LANDLOCK_RESTRICT_SELF_LOG__EXEC_ flags