From: Al Viro Date: Wed, 17 Oct 2018 14:23:26 +0000 (+0100) Subject: cachefiles: fix the race between cachefiles_bury_object() and rmdir(2) X-Git-Tag: v4.14.80~21 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ddb595dfe47278fd8ff3fd171b3729ec45d51b74;p=platform%2Fkernel%2Flinux-exynos.git 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 --- diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c index 5f2f67d..f6ed795f 100644 --- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -340,7 +340,7 @@ 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);