kernel/linux.git/security/landlock/task.c, branch v7.2-rc1

landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path

2026-06-13T21:14:59+00:00

LANDLOCK_SCOPE_SIGNAL must prevent a sandboxed process from signaling processes outside its Landlock domain. It can be bypassed through the asynchronous SIGIO delivery path. A sandboxed process that owns any file or socket can arm it with fcntl(fd, F_SETOWN, -pgid), fcntl(fd, F_SETSIG, SIGKILL) and O_ASYNC, so that an I/O event makes the kernel deliver the chosen signal to the whole process group. As the head of its process group's task list (the default position right after fork()) that group can also hold the non-sandboxed process that launched it, e.g. a supervisor or a security monitor. The sandbox can thus kill or signal the processes LANDLOCK_SCOPE_SIGNAL is meant to protect from it. The scope is enforced in hook_file_send_sigiotask() against the Landlock domain recorded at F_SETOWN time, not the live domain of the sender. control_current_fowner() decides whether to record that domain and skips recording it when the fowner target is in the caller's thread group, which is safe only for a single-task target (PIDTYPE_PID, PIDTYPE_TGID). For a process group (PIDTYPE_PGID) pid_task() returns only one member; recording is skipped whenever that member shares the caller's thread group, and hook_file_send_sigiotask() then lets the signal fan out to the whole group unchecked. Record the domain for every non single-process target so the scope is enforced against each group member at delivery time. That recording is necessary but not sufficient on its own: the kernel signals a process group through its members' thread-group leaders, and the leader of the registrant's own process can carry a different Landlock domain than the sibling thread that armed the owner. domain_is_scoped() would then deny that leader, even though commit 18eb75f3af40 ("landlock: Always allow signals between threads of the same process") requires same-process delivery to be allowed. hook_task_kill() avoids this by evaluating same_thread_group() live, per recipient; the SIGIO path instead delegates the whole decision to a single registration-time check, which a process-group fan-out cannot honor. So also record the registrant's thread group next to its domain and exempt it at delivery: hook_file_send_sigiotask() allows the signal whenever the recipient belongs to the registrant's own process, restoring the same-process guarantee while keeping out-of-domain group members blocked. The direct kill() path (hook_task_kill) already evaluates the live domain and is unaffected. Fixes: 18eb75f3af40 ("landlock: Always allow signals between threads of the same process") Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Reviewed-by: Günther Noack Link: https://patch.msgid.link/56bffc24f3d0d08b45a686a48e99766b0a0821fa.1780614610.git.hexlabsecurity@proton.me [mic: Check pid_type earlier and improve comment, fix commit message, fix comment formatting] Signed-off-by: Mickaël Salaün

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: 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: Improve the comment for domain_is_scoped

2025-12-29T15:19:39+00:00

Currently it is not obvious what "scoped" mean, and the fact that the function returns true when access should be denied is slightly surprising and in need of documentation. Cc: Tahera Fahimi Signed-off-by: Tingmao Wang Link: https://lore.kernel.org/r/06393bc18aee5bc278df5ef31c64a05b742ebc10.1766885035.git.m@maowtm.org [mic: Fix formatting and improve consistency] Signed-off-by: Mickaël Salaün

landlock: Clean up hook_ptrace_access_check()

2025-12-26T19:39:01+00:00

Make variable's scope minimal in hook_ptrace_access_check(). Cc: Günther Noack Link: https://lore.kernel.org/r/20251219193855.825889-3-mic@digikod.net Reviewed-by: Günther Noack 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: Add AUDIT_LANDLOCK_ACCESS and log ptrace denials

2025-03-26T12:59:38+00:00

Add a new AUDIT_LANDLOCK_ACCESS record type dedicated to an access request denied by a Landlock domain. AUDIT_LANDLOCK_ACCESS indicates that something unexpected happened. For now, only denied access are logged, which means that any AUDIT_LANDLOCK_ACCESS record is always followed by a SYSCALL record with "success=no". However, log parsers should check this syscall property because this is the only sign that a request was denied. Indeed, we could have "success=yes" if Landlock would support a "permissive" mode. We could also add a new field to AUDIT_LANDLOCK_DOMAIN for this mode (see following commit). By default, the only logged access requests are those coming from the same executed program that enforced the Landlock restriction on itself. In other words, no audit record are created for a task after it called execve(2). This is required to avoid log spam because programs may only be aware of their own restrictions, but not the inherited ones. Following commits will allow to conditionally generate AUDIT_LANDLOCK_ACCESS records according to dedicated landlock_restrict_self(2)'s flags. The AUDIT_LANDLOCK_ACCESS message contains: - the "domain" ID restricting the action on an object, - the "blockers" that are missing to allow the requested access, - a set of fields identifying the related object (e.g. task identified with "opid" and "ocomm"). The blockers are implicit restrictions (e.g. ptrace), or explicit access rights (e.g. filesystem), or explicit scopes (e.g. signal). This field contains a list of at least one element, each separated with a comma. The initial blocker is "ptrace", which describe all implicit Landlock restrictions related to ptrace (e.g. deny tracing of tasks outside a sandbox). Add audit support to ptrace_access_check and ptrace_traceme hooks. For the ptrace_access_check case, we log the current/parent domain and the child task. For the ptrace_traceme case, we log the parent domain and the current/child task. Indeed, the requester and the target are the current task, but the action would be performed by the parent task. Audit event sample: type=LANDLOCK_ACCESS msg=audit(1729738800.349:44): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd" type=SYSCALL msg=audit(1729738800.349:44): arch=c000003e syscall=101 success=no [...] pid=300 auid=0 A following commit adds user documentation. Add KUnit tests to check reading of domain ID relative to layer level. The quick return for non-landlocked tasks is moved from task_ptrace() to each LSM hooks. It is not useful to inline the audit_enabled check because other computation are performed by landlock_log_denial(). Use scoped guards for RCU read-side critical sections. Cc: Günther Noack Acked-by: Paul Moore Link: https://lore.kernel.org/r/20250320190717.2287696-10-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Prepare to use credential instead of domain for fowner

2025-03-26T12:59:37+00:00

This cosmetic change is needed for audit support, specifically to be able to filter according to cross-execution boundaries. struct landlock_file_security's size stay the same for now but it will increase with struct landlock_cred_security's size. Only save Landlock domain in hook_file_set_fowner() if the current domain has LANDLOCK_SCOPE_SIGNAL, which was previously done for each hook_file_send_sigiotask() calls. This should improve a bit performance. Replace hardcoded LANDLOCK_SCOPE_SIGNAL with the signal_scope.scope variable. Use scoped guards for RCU read-side critical sections. Cc: Günther Noack Link: https://lore.kernel.org/r/20250320190717.2287696-8-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Prepare to use credential instead of domain for scope

2025-03-26T12:59:36+00:00

This cosmetic change that is needed for audit support, specifically to be able to filter according to cross-execution boundaries. Replace hardcoded LANDLOCK_SCOPE_SIGNAL with the signal_scope.scope variable. Use scoped guards for RCU read-side critical sections. Cc: Günther Noack Link: https://lore.kernel.org/r/20250320190717.2287696-7-mic@digikod.net [mic: Update headers] Signed-off-by: Mickaël Salaün