From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:41338 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732912AbeKIHrj (ORCPT ); Fri, 9 Nov 2018 02:47:39 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , David Howells Subject: [PATCH 4.18 07/34] cachefiles: fix the race between cachefiles_bury_object() and rmdir(2) Date: Thu, 8 Nov 2018 13:52:36 -0800 Message-Id: <20181108215139.380698722@linuxfoundation.org> In-Reply-To: <20181108215138.892971755@linuxfoundation.org> References: <20181108215138.892971755@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro 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(-) --- 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);