kernel/linux.git/security/landlock/syscalls.c, branch v7.1-rc5

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: 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: Add errata documentation section

2026-02-06T16:54:43+00:00

Add errata section with code examples for querying errata and a warning that most applications should not check errata. Use kernel-doc directives to include errata descriptions from the header files instead of manual links. Also enhance existing DOC sections in security/landlock/errata/abi-*.h files with Impact sections, and update the code comment in syscalls.c to remind developers to update errata documentation when applicable. This addresses the gap where the kernel implements errata tracking but provides no user-facing documentation on how to use it, while improving the existing technical documentation in-place rather than duplicating it. Signed-off-by: Samasth Norway Ananda Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260128031814.2945394-3-samasth.norway.ananda@oracle.com [mic: Cosmetic fix] Signed-off-by: Mickaël Salaün

landlock: Multithreading support for landlock_restrict_self()

2026-02-06T16:54:37+00:00

Introduce the LANDLOCK_RESTRICT_SELF_TSYNC flag. With this flag, a given Landlock ruleset is applied to all threads of the calling process, instead of only the current one. Without this flag, multithreaded userspace programs currently resort to using the nptl(7)/libpsx hack for multithreaded policy enforcement, which is also used by libcap and for setuid(2). Using this userspace-based scheme, the threads of a process enforce the same Landlock policy, but the resulting Landlock domains are still separate. The domains being separate causes multiple problems: * When using Landlock's "scoped" access rights, the domain identity is used to determine whether an operation is permitted. As a result, when using LANLDOCK_SCOPE_SIGNAL, signaling between sibling threads stops working. This is a problem for programming languages and frameworks which are inherently multithreaded (e.g. Go). * In audit logging, the domains of separate threads in a process will get logged with different domain IDs, even when they are based on the same ruleset FD, which might confuse users. Cc: Andrew G. Morgan Cc: John Johansen Cc: Paul Moore Suggested-by: Jann Horn Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20251127115136.3064948-2-gnoack@google.com [mic: Fix restrict_self_flags test, clean up Makefile, allign comments, reduce local variable scope, add missing includes] Closes: https://github.com/landlock-lsm/linux/issues/2 Signed-off-by: Mickaël Salaün

landlock: opened file never has a negative dentry

2025-06-17T22:03:57+00:00

Reviewed-by: Christian Brauner Acked-by: Mickaël Salaün Signed-off-by: Al Viro

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: Fix documentation for landlock_restrict_self(2)

2025-04-17T09:09:10+00:00

Fix, deduplicate, and improve rendering of landlock_restrict_self(2)'s flags documentation. The flags are now rendered like the syscall's parameters and description. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250416154716.1799902-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Fix documentation for landlock_create_ruleset(2)

2025-04-17T09:09:07+00:00

Move and fix the flags documentation, and improve formatting. It makes more sense and it eases maintenance to document syscall flags in landlock.h, where they are defined. This is already the case for landlock_restrict_self(2)'s flags. The flags are now rendered like the syscall's parameters and description. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250416154716.1799902-1-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Add LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF

2025-03-26T12:59:43+00:00

Add LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF for the case of sandboxer tools, init systems, or runtime containers launching programs sandboxing themselves in an inconsistent way. Setting this flag should only depends on runtime configuration (i.e. not hardcoded). We don't create a new ruleset's option because this should not be part of the security policy: only the task that enforces the policy (not the one that create it) knows if itself or its children may request denied actions. This is the first and only flag that can be set without actually restricting the caller (i.e. without providing a ruleset). Extend struct landlock_cred_security with a u8 log_subdomains_off. struct landlock_file_security is still 16 bytes. Cc: Günther Noack Cc: Paul Moore Closes: https://github.com/landlock-lsm/linux/issues/3 Link: https://lore.kernel.org/r/20250320190717.2287696-19-mic@digikod.net [mic: Fix comment] Signed-off-by: Mickaël Salaün