kernel/linux.git/security/landlock, branch master

landlock: Clarify BUILD_BUG_ON check in scoping logic

2026-04-07T16:51:07+00:00

The BUILD_BUG_ON check in domain_is_scoped() and unmask_scoped_access() should check that the loop that counts down client_layer finishes. We therefore check that the numbers LANDLOCK_MAX_NUM_LAYERS-1 and -1 are both representable by that integer. If they are representable, the numbers in between are representable too, and the loop finishes. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20260327164838.38231-6-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün

landlock: Control pathname UNIX domain socket resolution by path

2026-04-07T16:51:06+00:00

* Add a new access right LANDLOCK_ACCESS_FS_RESOLVE_UNIX, which controls the lookup operations for named UNIX domain sockets. The resolution happens during connect() and sendmsg() (depending on socket type). * Change access_mask_t from u16 to u32 (see below) * Hook into the path lookup in unix_find_bsd() in af_unix.c, using a LSM hook. Make policy decisions based on the new access rights * Increment the Landlock ABI version. * Minor test adaptations to keep the tests working. * Document the design rationale for scoped access rights, and cross-reference it from the header documentation. With this access right, access is granted if either of the following conditions is met: * The target socket's filesystem path was allow-listed using a LANDLOCK_RULE_PATH_BENEATH rule, *or*: * The target socket was created in the same Landlock domain in which LANDLOCK_ACCESS_FS_RESOLVE_UNIX was restricted. In case of a denial, connect() and sendmsg() return EACCES, which is the same error as it is returned if the user does not have the write bit in the traditional UNIX file system permissions of that file. The access_mask_t type grows from u16 to u32 to make space for the new access right. This also doubles the size of struct layer_access_masks from 32 byte to 64 byte. To avoid memory layout inconsistencies between architectures (especially m68k), pack and align struct access_masks [2]. Document the (possible future) interaction between scoped flags and other access rights in struct landlock_ruleset_attr, and summarize the rationale, as discussed in code review leading up to [3]. This feature was created with substantial discussion and input from Justin Suess, Tingmao Wang and Mickaël Salaün. Cc: Tingmao Wang Cc: Justin Suess Cc: Kuniyuki Iwashima Suggested-by: Jann Horn Link[1]: https://github.com/landlock-lsm/linux/issues/36 Link[2]: https://lore.kernel.org/all/20260401.Re1Eesu1Yaij@digikod.net/ Link[3]: https://lore.kernel.org/all/20260205.8531e4005118@gnoack.org/ Signed-off-by: Günther Noack Acked-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20260327164838.38231-5-gnoack3000@gmail.com [mic: Fix kernel-doc formatting, pack and align access_masks] Signed-off-by: Mickaël Salaün

landlock: Use mem_is_zero() in is_layer_masks_allowed()

2026-04-07T16:51:06+00:00

This is equivalent, but expresses the intent a bit clearer. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20260327164838.38231-3-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün

landlock: Fix kernel-doc warning for pointer-to-array parameters

2026-04-07T16:51:05+00:00

The insert_rule() and create_rule() functions take a pointer-to-flexible-array parameter declared as: const struct landlock_layer (*const layers)[] The kernel-doc parser cannot handle a qualifier between * and the parameter name in this syntax, producing spurious "Invalid param" and "not described" warnings. Remove the const qualifier of the "layers" argument to avoid this parsing issue. Cc: Günther Noack Cc: Jonathan Corbet Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260310172004.1839864-1-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Fix formatting in tsync.c

2026-04-07T16:51:04+00:00

Fix comment formatting in tsync.c to fit in 80 columns. Cc: Günther Noack Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260304193134.250495-4-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Improve kernel-doc "Return:" section consistency

2026-04-07T16:51:04+00:00

The canonical kernel-doc form is "Return:" (singular, without trailing "s"). Normalize all existing "Returns:" occurrences across the Landlock source tree to the canonical form. Also fix capitalization for consistency. Balance descriptions to describe all possible returned values. Consolidate bullet-point return descriptions into inline text for functions with simple two-value or three-value returns for consistency. Cc: Günther Noack Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260304193134.250495-3-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Add missing kernel-doc "Return:" sections

2026-04-07T16:51:03+00:00

The kernel-doc -Wreturn check warns about functions with documentation comments that lack a "Return:" section. Add "Return:" documentation to all functions missing it so that kernel-doc -Wreturn passes cleanly. Convert existing function descriptions into a formal "Return:" section. Also fix the inaccurate return documentation for landlock_merge_ruleset() which claimed to return @parent directly, and document the previously missing ERR_PTR() error return path. Document the ABI version and errata return paths for landlock_create_ruleset() which were previously only implied by the prose. Cc: Günther Noack Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260304193134.250495-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Allow TSYNC with LOG_SUBDOMAINS_OFF and fd=-1

2026-04-07T16:51:00+00:00

LANDLOCK_RESTRICT_SELF_TSYNC does not allow LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF with ruleset_fd=-1, preventing a multithreaded process from atomically propagating subdomain log muting to all threads without creating a domain layer. Relax the fd=-1 condition to accept TSYNC alongside LOG_SUBDOMAINS_OFF, and update the documentation accordingly. Add flag validation tests for all TSYNC combinations with ruleset_fd=-1, and audit tests verifying both transition directions: muting via TSYNC (logged to not logged) and override via TSYNC (not logged to logged). Cc: Günther Noack Cc: stable@vger.kernel.org Fixes: 42fc7e6543f6 ("landlock: Multithreading support for landlock_restrict_self()") Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260407164107.2012589-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Fix LOG_SUBDOMAINS_OFF inheritance across fork()

2026-04-07T16:50:56+00:00

hook_cred_transfer() only copies the Landlock security blob when the source credential has a domain. This is inconsistent with landlock_restrict_self() which can set LOG_SUBDOMAINS_OFF on a credential without creating a domain (via the ruleset_fd=-1 path): the field is committed but not preserved across fork() because the child's prepare_creds() calls hook_cred_transfer() which skips the copy when domain is NULL. This breaks the documented use case where a process mutes subdomain logs before forking sandboxed children: the children lose the muting and their domains produce unexpected audit records. Fix this by unconditionally copying the Landlock credential blob. Cc: Günther Noack Cc: Jann Horn Cc: stable@vger.kernel.org Fixes: ead9079f7569 ("landlock: Add LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF") Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260407164107.2012589-1-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Clean up interrupted thread logic in TSYNC

2026-03-10T17:22:58+00:00

In landlock_restrict_sibling_threads(), when the calling thread is interrupted while waiting for sibling threads to prepare, it executes a recovery path. Previously, this path included a wait_for_completion() call on all_prepared to prevent a Use-After-Free of the local shared_ctx. However, this wait is redundant. Exiting the main do-while loop already leads to a bottom cleanup section that unconditionally waits for all_finished. Therefore, replacing the wait with a simple break is safe, prevents UAF, and correctly unblocks the remaining task_works. Clean up the error path by breaking the loop and updating the surrounding comments to accurately reflect the state machine. Suggested-by: Günther Noack Signed-off-by: Yihan Ding Tested-by: Günther Noack Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260306021651.744723-3-dingyihan@uniontech.com Signed-off-by: Mickaël Salaün