From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:46488 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753657AbdHOLAo (ORCPT ); Tue, 15 Aug 2017 07:00:44 -0400 From: Jan Kara To: Paul Moore Cc: linux-audit@redhat.com, tonyj@suse.de, Jan Kara , stable@vger.kernel.org Subject: [PATCH 1/2] audit: Fix use after free in audit_remove_watch_rule() Date: Tue, 15 Aug 2017 13:00:36 +0200 Message-Id: <20170815110037.30170-2-jack@suse.cz> In-Reply-To: <20170815110037.30170-1-jack@suse.cz> References: <20170815110037.30170-1-jack@suse.cz> Sender: stable-owner@vger.kernel.org List-ID: audit_remove_watch_rule() drops watch's reference to parent but then continues to work with it. That is not safe as parent can get freed once we drop our reference. The following is a trivial reproducer: mount -o loop image /mnt touch /mnt/file auditctl -w /mnt/file -p wax umount /mnt auditctl -D Grab our own reference in audit_remove_watch_rule() earlier to make sure mark does not get freed under us. CC: stable@vger.kernel.org Reported-by: Tony Jones Signed-off-by: Jan Kara --- kernel/audit_watch.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c index 62d686d96581..ed748ee40029 100644 --- a/kernel/audit_watch.c +++ b/kernel/audit_watch.c @@ -457,13 +457,15 @@ void audit_remove_watch_rule(struct audit_krule *krule) list_del(&krule->rlist); if (list_empty(&watch->rules)) { + /* + * audit_remove_watch() drops our reference to 'parent' which + * can get freed. Grab our own reference to be safe. + */ + audit_get_parent(parent); audit_remove_watch(watch); - - if (list_empty(&parent->watches)) { - audit_get_parent(parent); + if (list_empty(&parent->watches)) fsnotify_destroy_mark(&parent->mark, audit_watch_group); - audit_put_parent(parent); - } + audit_put_parent(parent); } } -- 2.12.3