diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2025-04-27 15:41:51 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-06-04 14:40:18 +0200 |
| commit | 9b0915e72b3cf52474dcee0b24a2f99d93e604a3 (patch) | |
| tree | bcdf0e5065a1a99c90385f7d7a02fb25a8b497ad | |
| parent | a58442f75be49c2be28a6eba387f5dbb1b11395c (diff) | |
__legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock
[ Upstream commit 250cf3693060a5f803c5f1ddc082bb06b16112a9 ]
... or we risk stealing final mntput from sync umount - raising mnt_count
after umount(2) has verified that victim is not busy, but before it
has set MNT_SYNC_UMOUNT; in that case __legitimize_mnt() doesn't see
that it's safe to quietly undo mnt_count increment and leaves dropping
the reference to caller, where it'll be a full-blown mntput().
Check under mount_lock is needed; leaving the current one done before
taking that makes no sense - it's nowhere near common enough to bother
with.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | fs/namespace.c | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 0dcd57a75ad4..211a81240680 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -632,12 +632,8 @@ int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) smp_mb(); // see mntput_no_expire() and do_umount() if (likely(!read_seqretry(&mount_lock, seq))) return 0; - if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { - mnt_add_count(mnt, -1); - return 1; - } lock_mount_hash(); - if (unlikely(bastard->mnt_flags & MNT_DOOMED)) { + if (unlikely(bastard->mnt_flags & (MNT_SYNC_UMOUNT | MNT_DOOMED))) { mnt_add_count(mnt, -1); unlock_mount_hash(); return 1; |