From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75CAEC54FD0 for ; Thu, 23 Apr 2020 23:11:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 573EE20784 for ; Thu, 23 Apr 2020 23:11:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728455AbgDWXLa (ORCPT ); Thu, 23 Apr 2020 19:11:30 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:50156 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728530AbgDWXGw (ORCPT ); Thu, 23 Apr 2020 19:06:52 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1jRkvb-0004n6-0u; Fri, 24 Apr 2020 00:06:43 +0100 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1jRkvW-00E6wt-PO; Fri, 24 Apr 2020 00:06:38 +0100 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, Denis Kirjanov , syzbot+2b2ef983f973e5c40943@syzkaller.appspotmail.com, "Takashi Iwai" Date: Fri, 24 Apr 2020 00:06:54 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 187/245] ALSA: seq: Fix racy access for queue timer in proc read In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.83-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 60adcfde92fa40fcb2dbf7cc52f9b096e0cd109a upstream. snd_seq_info_timer_read() reads the information of the timer assigned for each queue, but it's done in a racy way which may lead to UAF as spotted by syzkaller. This patch applies the missing q->timer_mutex lock while accessing the timer object as well as a slight code change to adapt the standard coding style. Reported-by: syzbot+2b2ef983f973e5c40943@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/20200115203733.26530-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/core/seq/seq_timer.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -484,15 +484,19 @@ void snd_seq_info_timer_read(struct snd_ q = queueptr(idx); if (q == NULL) continue; - if ((tmr = q->timer) == NULL || - (ti = tmr->timeri) == NULL) { - queuefree(q); - continue; - } + mutex_lock(&q->timer_mutex); + tmr = q->timer; + if (!tmr) + goto unlock; + ti = tmr->timeri; + if (!ti) + goto unlock; snd_iprintf(buffer, "Timer for queue %i : %s\n", q->queue, ti->timer->name); resolution = snd_timer_resolution(ti) * tmr->ticks; snd_iprintf(buffer, " Period time : %lu.%09lu\n", resolution / 1000000000, resolution % 1000000000); snd_iprintf(buffer, " Skew : %u / %u\n", tmr->skew, tmr->skew_base); +unlock: + mutex_unlock(&q->timer_mutex); queuefree(q); } }