4.18-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
commit 169b803397499be85bdd1e3d07d6f5e3d4bd669e upstream.
the victim might've been rmdir'ed just before the lock_rename(); unlike the normal callers, we do not look the source up after the parents are locked - we know it beforehand and just recheck that it's still the child of what used to be its parent. Unfortunately, the check is too weak - we don't spot a dead directory since its ->d_parent is unchanged, dentry is positive, etc. So we sail all the way to ->rename(), with hosting filesystems _not_ expecting to be asked renaming an rmdir'ed subdirectory.
The fix is easy, fortunately - the lock on parent is sufficient for making IS_DEADDIR() on child safe.
Cc: stable@vger.kernel.org Fixes: 9ae326a69004 (CacheFiles: A cache that backs onto a mounted filesystem) Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/cachefiles/namei.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -343,7 +343,7 @@ try_again: trap = lock_rename(cache->graveyard, dir);
/* do some checks before getting the grave dentry */ - if (rep->d_parent != dir) { + if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) { /* the entry was probably culled when we dropped the parent dir * lock */ unlock_rename(cache->graveyard, dir);