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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 5F020C433F5 for ; Sun, 26 Aug 2018 06:46:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B9CB2170B for ; Sun, 26 Aug 2018 06:46:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B9CB2170B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727502AbeHZK2A (ORCPT ); Sun, 26 Aug 2018 06:28:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:53622 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726245AbeHZK2A (ORCPT ); Sun, 26 Aug 2018 06:28:00 -0400 Received: from localhost (5355525A.cm-6-6b.dynamic.ziggo.nl [83.85.82.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 9ACA79D3; Sun, 26 Aug 2018 06:46:24 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+619d9f40141d826b097e@syzkaller.appspotmail.com, Takashi Iwai Subject: [PATCH 3.18 08/56] ALSA: virmidi: Fix too long output trigger loop Date: Sun, 26 Aug 2018 08:44:29 +0200 Message-Id: <20180826064232.682300338@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180826064232.320669119@linuxfoundation.org> References: <20180826064232.320669119@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 50e9ffb1996a5d11ff5040a266585bad4ceeca0a upstream. The virmidi output trigger tries to parse the all available bytes and process sequencer events as much as possible. In a normal situation, this is supposed to be relatively short, but a program may give a huge buffer and it'll take a long time in a single spin lock, which may eventually lead to a soft lockup. This patch simply adds a workaround, a cond_resched() call in the loop if applicable. A better solution would be to move the event processor into a work, but let's put a duct-tape quickly at first. Reported-and-tested-by: Dae R. Jeong Reported-by: syzbot+619d9f40141d826b097e@syzkaller.appspotmail.com Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/seq/seq_virmidi.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/sound/core/seq/seq_virmidi.c +++ b/sound/core/seq/seq_virmidi.c @@ -163,6 +163,7 @@ static void snd_virmidi_output_trigger(s int count, res; unsigned char buf[32], *pbuf; unsigned long flags; + bool check_resched = !in_atomic(); if (up) { vmidi->trigger = 1; @@ -200,6 +201,15 @@ static void snd_virmidi_output_trigger(s vmidi->event.type = SNDRV_SEQ_EVENT_NONE; } } + if (!check_resched) + continue; + /* do temporary unlock & cond_resched() for avoiding + * CPU soft lockup, which may happen via a write from + * a huge rawmidi buffer + */ + spin_unlock_irqrestore(&substream->runtime->lock, flags); + cond_resched(); + spin_lock_irqsave(&substream->runtime->lock, flags); } out: spin_unlock_irqrestore(&substream->runtime->lock, flags);