diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2025-04-27 15:41:51 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-29 11:03:13 +0200 |
| commit | 8cafd7266fa02e0863bacbf872fe635c0b9725eb (patch) | |
| tree | 18b02f588e58cf4427108ab69d0512193112c8ba | |
| parent | a0c50c9f9c912507ef8111ba5d5e595b7e699d61 (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 c3c1e8c644f2..c1ac585e41e3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -750,12 +750,8 @@ 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; |