kernel/linux.git/security/landlock, branch v6.12.107

landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path

2026-08-03T09:17:33+00:00

[ Upstream commit 4b80320ca7ed03d6e683f95b6066565dc97b9f92 ] 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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

landlock: Prepare to use credential instead of domain for fowner

2026-08-03T09:17:33+00:00

[ Upstream commit 79625f1b3a3df63d3289a0781fdf121bc42966f7 ] 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 Stable-dep-of: 4b80320ca7ed ("landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

landlock: Fix unmarked concurrent access to socket family

2026-07-24T14:11:02+00:00

[ Upstream commit 0ce4243509d1580349dd0d50624036d6b097e958 ] Socket family is read (twice) in a context where the socket is not locked, so another thread can setsockopt(IPV6_ADDRFORM) to write it concurrently. Add needed READ_ONCE() annotation. Use the proper macro to access __sk_common.skc_family like everywhere else. Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect") Signed-off-by: Matthieu Buffet Link: https://patch.msgid.link/20260609211511.85630-1-matthieu@buffet.re Link: https://patch.msgid.link/20260609211511.85630-2-matthieu@buffet.re [mic: Squash two patches, move variable to ease backport, fix comment formatting] Signed-off-by: Mickaël Salaün Signed-off-by: Sasha Levin

landlock: Fix TCP handling of short AF_UNSPEC addresses

2026-06-01T15:46:33+00:00

[ Upstream commit e4d82cbce2258f454634307fdabf33aa46b61ab0 ] current_check_access_socket() treats AF_UNSPEC addresses as AF_INET ones, and only later adds special case handling to allow connect(AF_UNSPEC), and on IPv4 sockets bind(AF_UNSPEC+INADDR_ANY). This would be fine except AF_UNSPEC addresses can be as short as a bare AF_UNSPEC sa_family_t field, and nothing more. The AF_INET code path incorrectly enforces a length of sizeof(struct sockaddr_in) instead. Move AF_UNSPEC edge case handling up inside the switch-case, before the address is (potentially incorrectly) treated as AF_INET. Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect") Signed-off-by: Matthieu Buffet Link: https://lore.kernel.org/r/20251027190726.626244-4-matthieu@buffet.re Signed-off-by: Mickaël Salaün [ There was a conflict due to missing commit 9f74411a40ce ("landlock: Log TCP bind and connect denials") ] Signed-off-by: Maximilian Heyne Signed-off-by: Sasha Levin

fdget(), trivial conversions

2026-05-23T11:04:35+00:00

[ Upstream commit 6348be02eead77bdd1562154ed6b3296ad3b3750 ] fdget() is the first thing done in scope, all matching fdput() are immediately followed by leaving the scope. Reviewed-by: Christian Brauner Signed-off-by: Al Viro Stable-dep-of: 66052a768d47 ("fanotify: call fanotify_events_supported() before path_permission() and security_path_notify()") Signed-off-by: Sasha Levin

landlock: Fix handling of disconnected directories

2026-04-02T11:09:51+00:00

[ 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 (cherry picked from commit 49c9e09d961025b22e61ef9ad56aa1c21b6ce2f1) Signed-off-by: Harshit Mogalapalli Signed-off-by: Greg Kroah-Hartman

landlock: Optimize file path walks and prepare for audit support

2026-04-02T11:09:51+00:00

[ Upstream commit d617f0d72d8041c7099fd04a62db0f0fa5331c1a ] Always synchronize access_masked_parent* with access_request_parent* according to allowed_parent*. This is required for audit support to be able to get back to the reason of denial. In a rename/link action, instead of always checking a rule two times for the same parent directory of the source and the destination files, only check it when an action on a child was not already allowed. This also enables us to keep consistent allowed_parent* status, which is required to get back to the reason of denial. For internal mount points, only upgrade allowed_parent* to true but do not wrongfully set both of them to false otherwise. This is also required to get back to the reason of denial. This does not impact the current behavior but slightly optimize code and prepare for audit support that needs to know the exact reason why an access was denied. Cc: Günther Noack Link: https://lore.kernel.org/r/20250108154338.1129069-14-mic@digikod.net Signed-off-by: Mickaël Salaün (cherry picked from commit d617f0d72d8041c7099fd04a62db0f0fa5331c1a) Stable-dep-of: 49c9e09d9610 ("landlock: Fix handling of disconnected directories") Signed-off-by: Harshit Mogalapalli Signed-off-by: Greg Kroah-Hartman

landlock: Prepare to add second errata

2025-04-20T08:15:56+00:00

commit 6d9ac5e4d70eba3e336f9809ba91ab2c49de6d87 upstream. Potentially include errata for Landlock ABI v5 (Linux 6.10) and v6 (Linux 6.12). That will be useful for the following signal scoping erratum. As explained in errata.h, this commit should be backportable without conflict down to ABI v5. It must then not include the errata/abi-6.h file. Fixes: 54a6e6bbf3be ("landlock: Add signal scoping") Cc: Günther Noack Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250318161443.279194-5-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Always allow signals between threads of the same process

2025-04-20T08:15:55+00:00

commit 18eb75f3af40be1f0fc2025d4ff821711222a2fd upstream. Because Linux credentials are managed per thread, user space relies on some hack to synchronize credential update across threads from the same process. This is required by the Native POSIX Threads Library and implemented by set*id(2) wrappers and libcap(3) to use tgkill(2) to synchronize threads. See nptl(7) and libpsx(3). Furthermore, some runtimes like Go do not enable developers to have control over threads [1]. To avoid potential issues, and because threads are not security boundaries, let's relax the Landlock (optional) signal scoping to always allow signals sent between threads of the same process. This exception is similar to the __ptrace_may_access() one. hook_file_set_fowner() now checks if the target task is part of the same process as the caller. If this is the case, then the related signal triggered by the socket will always be allowed. Scoping of abstract UNIX sockets is not changed because kernel objects (e.g. sockets) should be tied to their creator's domain at creation time. Note that creating one Landlock domain per thread puts each of these threads (and their future children) in their own scope, which is probably not what users expect, especially in Go where we do not control threads. However, being able to drop permissions on all threads should not be restricted by signal scoping. We are working on a way to make it possible to atomically restrict all threads of a process with the same domain [2]. Add erratum for signal scoping. Closes: https://github.com/landlock-lsm/go-landlock/issues/36 Fixes: 54a6e6bbf3be ("landlock: Add signal scoping") Fixes: c8994965013e ("selftests/landlock: Test signal scoping for threads") Depends-on: 26f204380a3c ("fs: Fix file_set_fowner LSM hook inconsistencies") Link: https://pkg.go.dev/kernel.org/pub/linux/libs/security/libcap/psx [1] Link: https://github.com/landlock-lsm/linux/issues/2 [2] Cc: Günther Noack Cc: Paul Moore Cc: Serge Hallyn Cc: Tahera Fahimi Cc: stable@vger.kernel.org Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20250318161443.279194-6-mic@digikod.net [mic: Add extra pointer check and RCU guard, and ease backport] Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Add erratum for TCP fix

2025-04-20T08:15:55+00:00

commit 48fce74fe209ba9e9b416d7100ccee546edc9fc6 upstream. Add erratum for the TCP socket identification fixed with commit 854277e2cc8c ("landlock: Fix non-TCP sockets restriction"). Fixes: 854277e2cc8c ("landlock: Fix non-TCP sockets restriction") Cc: Günther Noack Cc: Mikhail Ivanov Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250318161443.279194-4-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman