From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753839AbeE3Lmm (ORCPT ); Wed, 30 May 2018 07:42:42 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60670 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751827AbeE3LG6 (ORCPT ); Wed, 30 May 2018 07:06:58 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Nicolai Stange" , "=?UTF-8?Q?=E8=8C=83=E9=BE=99=E9=A3=9E?=" , "Takashi Iwai" Date: Wed, 30 May 2018 11:52:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 014/153] ALSA: seq: Don't allow resizing pool in use In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.102-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit d85739367c6d56e475c281945c68fdb05ca74b4c upstream. This is a fix for a (sort of) fallout in the recent commit d15d662e89fc ("ALSA: seq: Fix racy pool initializations") for CVE-2018-1000004. As the pool resize deletes the existing cells, it may lead to a race when another thread is writing concurrently, eventually resulting a UAF. A simple workaround is not to allow the pool resizing when the pool is in use. It's an invalid behavior in anyway. Fixes: d15d662e89fc ("ALSA: seq: Fix racy pool initializations") Reported-by: 范龙飞 Reported-by: Nicolai Stange Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/core/seq/seq_clientmgr.c | 3 +++ 1 file changed, 3 insertions(+) --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1917,6 +1917,9 @@ static int snd_seq_ioctl_set_client_pool (! snd_seq_write_pool_allocated(client) || info.output_pool != client->pool->size)) { if (snd_seq_write_pool_allocated(client)) { + /* is the pool in use? */ + if (atomic_read(&client->pool->counter)) + return -EBUSY; /* remove all existing cells */ snd_seq_pool_mark_closing(client->pool); snd_seq_queue_client_leave_cells(client->number);