kernel/linux.git/security/landlock/fs.c, branch v7.0.10

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: Optimize stack usage when !CONFIG_AUDIT

2025-12-29T15:19:35+00:00

Until now, each landlock_request struct were allocated on the stack, even if not really used, because is_access_to_paths_allowed() unconditionally modified the passed references. Even if the changed landlock_request variables are not used, the compiler is not smart enough to detect this case. To avoid this issue, explicitly disable the related code when CONFIG_AUDIT is not set, which enables elision of log_request_parent* and associated caller's stack variables thanks to dead code elimination. This makes it possible to reduce the stack frame by 32 bytes for the path_link and path_rename hooks, and by 20 bytes for most other filesystem hooks. Here is a summary of scripts/stackdelta before and after this change when CONFIG_AUDIT is disabled: current_check_refer_path 560 320 -240 current_check_access_path 328 184 -144 hook_file_open 328 184 -144 is_access_to_paths_allowed 376 360 -16 Also, add extra pointer checks to be more future-proof. Cc: Günther Noack Reported-by: Tingmao Wang Closes: https://lore.kernel.org/r/eb86863b-53b0-460b-b223-84dd31d765b9@maowtm.org Fixes: 2fc80c69df82 ("landlock: Log file-related denials") Link: https://lore.kernel.org/r/20251219142302.744917-2-mic@digikod.net Reviewed-by: Günther Noack [mic: Improve stack usage measurement accuracy with scripts/stackdelta] Signed-off-by: Mickaël Salaün

landlock: Fix formatting

2025-12-26T19:38:53+00:00

Format with clang-format -i security/landlock/*.[ch] Cc: Christian Brauner Cc: Günther Noack Cc: Mateusz Guzik Fixes: b4dbfd8653b3 ("Coccinelle-based conversion to use ->i_state accessors") Link: https://lore.kernel.org/r/20251219193855.825889-5-mic@digikod.net Reviewed-by: Günther Noack Signed-off-by: Mickaël Salaün

Merge tag 'landlock-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

2025-12-06T17:52:41+00:00

Pull landlock updates from Mickaël Salaün: "This mainly fixes handling of disconnected directories and adds new tests" * tag 'landlock-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: selftests/landlock: Add disconnected leafs and branch test suites selftests/landlock: Add tests for access through disconnected paths landlock: Improve variable scope landlock: Fix handling of disconnected directories selftests/landlock: Fix makefile header list landlock: Make docs in cred.h and domain.h visible landlock: Minor comments improvements

Merge tag 'vfs-6.19-rc1.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-01T17:02:34+00:00

Pull vfs inode updates from Christian Brauner: "Features: - Hide inode->i_state behind accessors. Open-coded accesses prevent asserting they are done correctly. One obvious aspect is locking, but significantly more can be checked. For example it can be detected when the code is clearing flags which are already missing, or is setting flags when it is illegal (e.g., I_FREEING when ->i_count > 0) - Provide accessors for ->i_state, converts all filesystems using coccinelle and manual conversions (btrfs, ceph, smb, f2fs, gfs2, overlayfs, nilfs2, xfs), and makes plain ->i_state access fail to compile - Rework I_NEW handling to operate without fences, simplifying the code after the accessor infrastructure is in place Cleanups: - Move wait_on_inode() from writeback.h to fs.h - Spell out fenced ->i_state accesses with explicit smp_wmb/smp_rmb for clarity - Cosmetic fixes to LRU handling - Push list presence check into inode_io_list_del() - Touch up predicts in __d_lookup_rcu() - ocfs2: retire ocfs2_drop_inode() and I_WILL_FREE usage - Assert on ->i_count in iput_final() - Assert ->i_lock held in __iget() Fixes: - Add missing fences to I_NEW handling" * tag 'vfs-6.19-rc1.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (22 commits) dcache: touch up predicts in __d_lookup_rcu() fs: push list presence check into inode_io_list_del() fs: cosmetic fixes to lru handling fs: rework I_NEW handling to operate without fences fs: make plain ->i_state access fail to compile xfs: use the new ->i_state accessors nilfs2: use the new ->i_state accessors overlayfs: use the new ->i_state accessors gfs2: use the new ->i_state accessors f2fs: use the new ->i_state accessors smb: use the new ->i_state accessors ceph: use the new ->i_state accessors btrfs: use the new ->i_state accessors Manual conversion to use ->i_state accessors of all places not covered by coccinelle Coccinelle-based conversion to use ->i_state accessors fs: provide accessors for ->i_state fs: spell out fenced ->i_state accesses with explicit smp_wmb/smp_rmb fs: move wait_on_inode() from writeback.h to fs.h fs: add missing fences to I_NEW handling ocfs2: retire ocfs2_drop_inode() and I_WILL_FREE usage ...

landlock: Improve variable scope

2025-11-28T17:27:06+00:00

This is now possible thanks to the disconnected directory fix. Cc: Günther Noack Cc: Song Liu Cc: Tingmao Wang Link: https://lore.kernel.org/r/20251128172200.760753-3-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Fix handling of disconnected directories

2025-11-28T17:27:04+00:00

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

landlock: Minor comments improvements

2025-11-26T19:20:21+00:00

This patch contains some small comment changes. The first three comments for ruleset.c, I sort of made along the way while working on / trying to understand Landlock, and the one from ruleset.h was from the hashtable patch but extracted here. In fs.c, one comment which I found would have been helpful to me when reading this. Signed-off-by: Tingmao Wang Link: https://lore.kernel.org/r/20250602134150.67189-1-m@maowtm.org Link: https://lore.kernel.org/r/20297185fd71ffbb5ce4fec14b38e5444c719c96.1748379182.git.m@maowtm.org [mic: Squash patches with updated description, cosmetic fixes] Signed-off-by: Mickaël Salaün

landlock: fix splats from iput() after it started calling might_sleep()

2025-11-12T09:47:42+00:00

At this point it is guaranteed this is not the last reference. However, a recent addition of might_sleep() at top of iput() started generating false-positives as it was executing for all values. Remedy the problem by using the newly introduced iput_not_last(). Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68d32659.a70a0220.4f78.0012.GAE@google.com/ Fixes: 2ef435a872ab ("fs: add might_sleep() annotation to iput() and more") Signed-off-by: Mateusz Guzik Link: https://patch.msgid.link/20251105212025.807549-2-mjguzik@gmail.com Reviewed-by: Mickaël Salaün Signed-off-by: Christian Brauner