kernel/linux.git/fs/notify, branch v6.12.91

fsnotify: fix inode reference leak in fsnotify_recalc_mask()

2026-05-23T11:04:52+00:00

[ Upstream commit 4aca914ac152f5d055ddcb36704d1e539ac08977 ] fsnotify_recalc_mask() fails to handle the return value of __fsnotify_recalc_mask(), which may return an inode pointer that needs to be released via fsnotify_drop_object() when the connector's HAS_IREF flag transitions from set to cleared. This manifests as a hung task with the following call trace: INFO: task umount:1234 blocked for more than 120 seconds. Call Trace: __schedule schedule fsnotify_sb_delete generic_shutdown_super kill_anon_super cleanup_mnt task_work_run do_exit do_group_exit The race window that triggers the iref leak: Thread A (adding mark) Thread B (removing mark) ────────────────────── ──────────────────────── fsnotify_add_mark_locked(): fsnotify_add_mark_list(): spin_lock(conn->lock) add mark_B(evictable) to list spin_unlock(conn->lock) return /* ---- gap: no lock held ---- */ fsnotify_detach_mark(mark_A): spin_lock(mark_A->lock) clear ATTACHED flag on mark_A spin_unlock(mark_A->lock) fsnotify_put_mark(mark_A) fsnotify_recalc_mask(): spin_lock(conn->lock) __fsnotify_recalc_mask(): /* mark_A skipped: ATTACHED cleared */ /* only mark_B(evictable) remains */ want_iref = false has_iref = true /* not yet cleared */ -> HAS_IREF transitions true -> false -> returns inode pointer spin_unlock(conn->lock) /* BUG: return value discarded! * iput() and fsnotify_put_sb_watched_objects() * are never called */ Fix this by deferring the transition true -> false of HAS_IREF flag from fsnotify_recalc_mask() (Thread A) to fsnotify_put_mark() (thread B). Fixes: c3638b5b1374 ("fsnotify: allow adding an inode mark without pinning inode") Signed-off-by: Xin Yin Signed-off-by: Amir Goldstein Link: https://patch.msgid.link/CAOQ4uxiPsbHb0o5voUKyPFMvBsDkG914FYDcs4C5UpBMNm0Vcg@mail.gmail.com Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

fanotify: call fanotify_events_supported() before path_permission() and security_path_notify()

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

[ Upstream commit 66052a768d4726a31e939b5ac902f2b0b452c8d5 ] The latter trigger LSM (e.g. SELinux) checks, which will log a denial when permission is denied, so it's better to do them after validity checks to avoid logging a denial when the operation would fail anyway. Fixes: 0b3b094ac9a7 ("fanotify: Disallow permission events for proc filesystem") Signed-off-by: Ondrej Mosnacek Reviewed-by: Amir Goldstein Reviewed-by: Paul Moore Link: https://patch.msgid.link/20260216150625.793013-3-omosnace@redhat.com Signed-off-by: Jan Kara 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

fanotify: fix false positive on permission events

2026-05-14T13:29:21+00:00

commit 7746e3bd4cc19b5092e00d32d676e329bfcb6900 upstream. fsnotify_get_mark_safe() may return false for a mark on an unrelated group, which results in bypassing the permission check. Fix by skipping over detached marks that are not in the current group. CC: stable@vger.kernel.org Fixes: abc77577a669 ("fsnotify: Provide framework for dropping SRCU lock in ->handle_event") Signed-off-by: Miklos Szeredi Link: https://patch.msgid.link/20260410144950.156160-1-mszeredi@redhat.com Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails

2026-05-07T04:09:39+00:00

commit 6a320935fa4293e9e599ec9f85dc9eb3be7029f8 upstream. When fsnotify_add_inode_mark_locked() fails in inotify_new_watch(), the error path calls inotify_remove_from_idr() but does not call dec_inotify_watches() to undo the preceding inc_inotify_watches(). This leaks a watch count, and repeated failures can exhaust the max_user_watches limit with -ENOSPC even when no watches are active. Prior to commit 1cce1eea0aff ("inotify: Convert to using per-namespace limits"), the watch count was incremented after fsnotify_add_mark_locked() succeeded, so this path was not affected. The conversion moved inc_inotify_watches() before the mark insertion without adding the corresponding rollback. Add the missing dec_inotify_watches() call in the error path. Fixes: 1cce1eea0aff ("inotify: Convert to using per-namespace limits") Cc: stable@vger.kernel.org Signed-off-by: Chia-Ming Chang Signed-off-by: robbieko Reviewed-by: Nikolay Borisov Link: https://patch.msgid.link/20260224093442.3076294-1-chiamingc@synology.com Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fsnotify: do not generate ACCESS/MODIFY events on child for special files

2026-01-08T09:14:24+00:00

commit 635bc4def026a24e071436f4f356ea08c0eed6ff upstream. inotify/fanotify do not allow users with no read access to a file to subscribe to events (e.g. IN_ACCESS/IN_MODIFY), but they do allow the same user to subscribe for watching events on children when the user has access to the parent directory (e.g. /dev). Users with no read access to a file but with read access to its parent directory can still stat the file and see if it was accessed/modified via atime/mtime change. The same is not true for special files (e.g. /dev/null). Users will not generally observe atime/mtime changes when other users read/write to special files, only when someone sets atime/mtime via utimensat(). Align fsnotify events with this stat behavior and do not generate ACCESS/MODIFY events to parent watchers on read/write of special files. The events are still generated to parent watchers on utimensat(). This closes some side-channels that could be possibly used for information exfiltration [1]. [1] https://snee.la/pdf/pubs/file-notification-attacks.pdf Reported-by: Sudheendra Raghav Neela CC: stable@vger.kernel.org Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fs/notify: call exportfs_encode_fid with s_umount

2025-10-29T13:08:55+00:00

commit a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a upstream. Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL | | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) [ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240 IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path. Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/ Fixes: c45beebfde34 ("ovl: support encoding fid from inode with no alias") Signed-off-by: Jakub Acs Cc: Jan Kara Cc: Amir Goldstein Cc: Miklos Szeredi Cc: Christian Brauner Cc: linux-unionfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fanotify: sanitize handle_type values when reporting fid

2025-08-15T10:13:51+00:00

[ Upstream commit 8631e01c2c5d1fe6705bcc0d733a0b7a17d3daac ] Unlike file_handle, type and len of struct fanotify_fh are u8. Traditionally, filesystem return handle_type < 0xff, but there is no enforecement for that in vfs. Add a sanity check in fanotify to avoid truncating handle_type if its value is > 0xff. Fixes: 7cdafe6cc4a6 ("exportfs: check for error return value from exportfs_encode_*()") Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Link: https://patch.msgid.link/20250627104835.184495-1-amir73il@gmail.com Signed-off-by: Sasha Levin

fix a leak in fcntl_dirnotify()

2025-07-24T06:56:30+00:00

[ Upstream commit fdfe0133473a528e3f5da69c35419ce6711d6b89 ] [into #fixes, unless somebody objects] Lifetime of new_dn_mark is controlled by that of its ->fsn_mark, pointed to by new_fsn_mark. Unfortunately, a failure exit had been inserted between the allocation of new_dn_mark and the call of fsnotify_init_mark(), ending up with a leak. Fixes: 1934b212615d "file: reclaim 24 bytes from f_owner" Signed-off-by: Al Viro Link: https://lore.kernel.org/20250712171843.GB1880847@ZenIV Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

fs: relax assertions on failure to encode file handles

2025-01-17T12:40:46+00:00

commit 974e3fe0ac61de85015bbe5a4990cf4127b304b2 upstream. Encoding file handles is usually performed by a filesystem >encode_fh() method that may fail for various reasons. The legacy users of exportfs_encode_fh(), namely, nfsd and name_to_handle_at(2) syscall are ready to cope with the possibility of failure to encode a file handle. There are a few other users of exportfs_encode_{fh,fid}() that currently have a WARN_ON() assertion when ->encode_fh() fails. Relax those assertions because they are wrong. The second linked bug report states commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") in v6.6 as the regressing commit, but this is not accurate. The aforementioned commit only increases the chances of the assertion and allows triggering the assertion with the reproducer using overlayfs, inotify and drop_caches. Triggering this assertion was always possible with other filesystems and other reasons of ->encode_fh() failures and more particularly, it was also possible with the exact same reproducer using overlayfs that is mounted with options index=on,nfs_export=on also on kernels < v6.6. Therefore, I am not listing the aforementioned commit as a Fixes commit. Backport hint: this patch will have a trivial conflict applying to v6.6.y, and other trivial conflicts applying to stable kernels < v6.6. Reported-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Tested-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-unionfs/671fd40c.050a0220.4735a.024f.GAE@google.com/ Reported-by: Dmitry Safonov Closes: https://lore.kernel.org/linux-fsdevel/CAGrbwDTLt6drB9eaUagnQVgdPBmhLfqqxAf3F+Juqy_o6oP8uw@mail.gmail.com/ Cc: stable@vger.kernel.org Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20241219115301.465396-1-amir73il@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman