From fdbbd418092845102fd8f21e3eadc8498b0bf38e Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 17 Oct 2018 15:23:26 +0100 Subject: cachefiles: fix the race between cachefiles_bury_object() and rmdir(2) 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 Signed-off-by: David Howells Signed-off-by: Greg Kroah-Hartman --- fs/cachefiles/namei.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/cachefiles') diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c index 80ed75bde04a..07e06145ea48 100644 --- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -317,7 +317,7 @@ 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); -- cgit v1.2.3