kernel/linux.git/security/landlock, branch v7.0-rc7

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

landlock: Serialize TSYNC thread restriction

2026-03-10T17:22:56+00:00

syzbot found a deadlock in landlock_restrict_sibling_threads(). When multiple threads concurrently call landlock_restrict_self() with sibling thread restriction enabled, they can deadlock by mutually queueing task_works on each other and then blocking in kernel space (waiting for the other to finish). Fix this by serializing the TSYNC operations within the same process using the exec_update_lock. This prevents concurrent invocations from deadlocking. We use down_write_trylock() and restart the syscall if the lock cannot be acquired immediately. This ensures that if a thread fails to get the lock, it will return to userspace, allowing it to process any pending TSYNC task_works from the lock holder, and then transparently restart the syscall. Fixes: 42fc7e6543f6 ("landlock: Multithreading support for landlock_restrict_self()") Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7ea2f5e9dfd468201817 Suggested-by: Günther Noack Suggested-by: Tingmao Wang Tested-by: Justin Suess Signed-off-by: Yihan Ding Tested-by: Günther Noack Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260306021651.744723-2-dingyihan@uniontech.com Signed-off-by: Mickaël Salaün

landlock: Improve TSYNC types

2026-03-04T17:28:11+00:00

Constify pointers when it makes sense. Consistently use size_t for loops, especially to match works->size type. Add new lines to improve readability. Cc: Jann Horn Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260217122341.2359582-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Fully release unused TSYNC work entries

2026-03-04T17:28:10+00:00

If task_work_add() failed, ctx->task is put but the tsync_works struct is not reset to its previous state. The first consequence is that the kernel allocates memory for dying threads, which could lead to user-accounted memory exhaustion (not very useful nor specific to this case). The second consequence is that task_work_cancel(), called by cancel_tsync_works(), can dereference a NULL task pointer. Fix this issues by keeping a consistent works->size wrt the added task work. This is done in a new tsync_works_trim() helper which also cleans up the shared_ctx and work fields. As a safeguard, add a pointer check to cancel_tsync_works() and update tsync_works_release() accordingly. Cc: Jann Horn Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260217122341.2359582-1-mic@digikod.net [mic: Replace memset() with compound literal] Signed-off-by: Mickaël Salaün

landlock: Fix formatting

2026-03-04T17:28:08+00:00

Auto-format with clang-format -i security/landlock/*.[ch] Cc: Günther Noack Cc: Kees Cook Fixes: 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types") Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20260303173632.88040-1-mic@digikod.net Signed-off-by: Mickaël Salaün

Convert 'alloc_flex' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This is the exact same thing as the 'alloc_obj()' version, only much smaller because there are a lot fewer users of the *alloc_flex() interface. As with alloc_obj() version, this was done entirely with mindless brute force, using the same script, except using 'flex' in the pattern rather than 'objs*'. Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

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: Add access_mask_subset() helper

2026-02-10T15:46:48+00:00

This helper function checks whether an access_mask_t has a subset of the bits enabled than another one. This expresses the intent a bit smoother in the code and does not cost us anything when it gets inlined. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20260206151154.97915-4-gnoack3000@gmail.com [mic: Improve subject] 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