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linux/fs/notify
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Amir Goldstein 73697928c8 fs: relax assertions on failure to encode file handles 
commit 974e3fe0ac 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 16aac5ad1f ("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 <dima@arista.com>
Closes: https://lore.kernel.org/linux-fsdevel/CAGrbwDTLt6drB9eaUagnQVgdPBmhLfqqxAf3F+Juqy_o6oP8uw@mail.gmail.com/
Cc: stable@vger.kernel.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20241219115301.465396-1-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Norbert Manthey <nmanthey@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-09-09 18:54:21 +02:00
..
dnotify dnotify: use fsnotify group lock helpers 2022-04-25 14:37:34 +02:00
fanotify fanotify: disallow mount/sb marks on kernel internal pseudo fs 2023-07-19 16:22:05 +02:00
inotify inotify: Avoid reporting event with invalid wd 2023-05-17 11:53:44 +02:00
fdinfo.c fs: relax assertions on failure to encode file handles 2025-09-09 18:54:21 +02:00
fdinfo.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fsnotify.c fsnotify: fix sending inotify event with unexpected filename 2024-12-14 19:53:59 +01:00
fsnotify.h fsnotify: clear PARENT_WATCHED flags lazily 2024-09-08 07:53:10 +02:00
group.c fsnotify: create helpers for group mark_mutex lock 2022-04-25 14:37:22 +02:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mark.c fsnotify: clear PARENT_WATCHED flags lazily 2024-09-08 07:53:10 +02:00
notification.c fsnotify: Pass group argument to free_event 2021-10-27 12:34:18 +02:00