Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tony Jones , Jan Kara , Paul Moore Subject: [PATCH 4.9 02/27] audit: Fix use after free in audit_remove_watch_rule() Date: Tue, 22 Aug 2017 12:13:34 -0700 Message-Id: <20170822191327.175562944@linuxfoundation.org> In-Reply-To: <20170822191327.078387788@linuxfoundation.org> References: <20170822191327.078387788@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit d76036ab47eafa6ce52b69482e91ca3ba337d6d6 upstream. 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. Reported-by: Tony Jones Signed-off-by: Jan Kara Tested-by: Tony Jones Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman --- kernel/audit_watch.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/kernel/audit_watch.c +++ b/kernel/audit_watch.c @@ -457,13 +457,15 @@ void audit_remove_watch_rule(struct audi 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); } }