kernel/linux.git/fs/notify, branch v6.1.168

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

2026-01-11T14:18:56+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: relax assertions on failure to encode file handles

2025-09-09T16:54:21+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: Norbert Manthey Signed-off-by: Greg Kroah-Hartman

fsnotify: fix sending inotify event with unexpected filename

2024-12-14T18:53:59+00:00

commit aa52c54da40d9eee3ba87c05cdcb0cd07c04fa13 upstream. We got a report that adding a fanotify filsystem watch prevents tail -f from receiving events. Reproducer: 1. Create 3 windows / login sessions. Become root in each session. 2. Choose a mounted filesystem that is pretty quiet; I picked /boot. 3. In the first window, run: fsnotifywait -S -m /boot 4. In the second window, run: echo data >> /boot/foo 5. In the third window, run: tail -f /boot/foo 6. Go back to the second window and run: echo more data >> /boot/foo 7. Observe that the tail command doesn't show the new data. 8. In the first window, hit control-C to interrupt fsnotifywait. 9. In the second window, run: echo still more data >> /boot/foo 10. Observe that the tail command in the third window has now printed the missing data. When stracing tail, we observed that when fanotify filesystem mark is set, tail does get the inotify event, but the event is receieved with the filename: read(4, "\1\0\0\0\2\0\0\0\0\0\0\0\20\0\0\0foo\0\0\0\0\0\0\0\0\0\0\0\0\0", 50) = 32 This is unexpected, because tail is watching the file itself and not its parent and is inconsistent with the inotify event received by tail when fanotify filesystem mark is not set: read(4, "\1\0\0\0\2\0\0\0\0\0\0\0\0\0\0\0", 50) = 16 The inteference between different fsnotify groups was caused by the fact that the mark on the sb requires the filename, so the filename is passed to fsnotify(). Later on, fsnotify_handle_event() tries to take care of not passing the filename to groups (such as inotify) that are interested in the filename only when the parent is watching. But the logic was incorrect for the case that no group is watching the parent, some groups are watching the sb and some watching the inode. Reported-by: Miklos Szeredi Fixes: 7372e79c9eb9 ("fanotify: fix logic of reporting name info with watched parent") Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

fsnotify: clear PARENT_WATCHED flags lazily

2024-09-08T05:53:10+00:00

[ Upstream commit 172e422ffea20a89bfdc672741c1aad6fbb5044e ] In some setups directories can have many (usually negative) dentries. Hence __fsnotify_update_child_dentry_flags() function can take a significant amount of time. Since the bulk of this function happens under inode->i_lock this causes a significant contention on the lock when we remove the watch from the directory as the __fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask() races with __fsnotify_update_child_dentry_flags() calls from __fsnotify_parent() happening on children. This can lead upto softlockup reports reported by users. Fix the problem by calling fsnotify_update_children_dentry_flags() to set PARENT_WATCHED flags only when parent starts watching children. When parent stops watching children, clear false positive PARENT_WATCHED flags lazily in __fsnotify_parent() for each accessed child. Suggested-by: Jan Kara Signed-off-by: Amir Goldstein Signed-off-by: Stephen Brennan Signed-off-by: Jan Kara Signed-off-by: Sasha Levin

fanotify: disallow mount/sb marks on kernel internal pseudo fs

2023-07-19T14:22:05+00:00

[ Upstream commit 69562eb0bd3e6bb8e522a7b254334e0fb30dff0c ] Hopefully, nobody is trying to abuse mount/sb marks for watching all anonymous pipes/inodes. I cannot think of a good reason to allow this - it looks like an oversight that dated back to the original fanotify API. Link: https://lore.kernel.org/linux-fsdevel/20230628101132.kvchg544mczxv2pm@quack3/ Fixes: 0ff21db9fcc3 ("fanotify: hooks the fanotify_mark syscall to the vfsmount code") Signed-off-by: Amir Goldstein Reviewed-by: Christian Brauner Signed-off-by: Jan Kara Message-Id: <20230629042044.25723-1-amir73il@gmail.com> Signed-off-by: Sasha Levin

inotify: Avoid reporting event with invalid wd

2023-05-17T09:53:44+00:00

commit c915d8f5918bea7c3962b09b8884ca128bfd9b0c upstream. When inotify_freeing_mark() races with inotify_handle_inode_event() it can happen that inotify_handle_inode_event() sees that i_mark->wd got already reset to -1 and reports this value to userspace which can confuse the inotify listener. Avoid the problem by validating that wd is sensible (and pretend the mark got removed before the event got generated otherwise). CC: stable@vger.kernel.org Fixes: 7e790dd5fc93 ("inotify: fix error paths in inotify_update_watch") Message-Id: <20230424163219.9250-1-jack@suse.cz> Reported-by: syzbot+4a06d4373fd52f0b2f9c@syzkaller.appspotmail.com Reviewed-by: Amir Goldstein Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman

Merge tag 'fsnotify-for_v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

2022-10-07T15:28:50+00:00

Pull fsnotify updates from Jan Kara: "Two cleanups for fsnotify code" * tag 'fsnotify-for_v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs: fanotify: Remove obsoleted fanotify_event_has_path() fsnotify: remove unused declaration

fanotify: Remove obsoleted fanotify_event_has_path()

2022-09-26T09:28:40+00:00

All uses of fanotify_event_has_path() have been removed since commit 9c61f3b560f5 ("fanotify: break up fanotify_alloc_event()"), now it is useless, so remove it. Link: https://lore.kernel.org/r/20220926023018.1505270-1-cuigaosheng1@huawei.com Signed-off-by: Gaosheng Cui Signed-off-by: Jan Kara

fsnotify: remove unused declaration

2022-09-09T09:40:03+00:00

fsnotify_alloc_event_holder() and fsnotify_destroy_event_holder() has been removed since commit 7053aee26a35 ("fsnotify: do not share events between notification groups"), so remove it. Reviewed-by: Ritesh Harjani (IBM) Signed-off-by: Gaosheng Cui Signed-off-by: Jan Kara

fs/notify: constify path

2022-09-01T21:37:29+00:00

Reviewed-by: Matthew Bobrowski Reviewed-by: Christian Brauner (Microsoft) Signed-off-by: Al Viro