From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754381Ab0BFPuc (ORCPT ); Sat, 6 Feb 2010 10:50:32 -0500 Received: from mout.perfora.net ([74.208.4.195]:54421 "EHLO mout.perfora.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750889Ab0BFPub (ORCPT ); Sat, 6 Feb 2010 10:50:31 -0500 Message-ID: <4B6D8ED2.5060107@nctritech.com> Date: Sat, 06 Feb 2010 10:46:26 -0500 From: "Jody@Tritech" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100111 Thunderbird/3.0.1 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: [PATCH] hda-intel: Avoid divide by zero crash Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V01U2FsdGVkX1/52/hn0vgyGkiniOiGbx/rAffJiFUYn2NDWPs uezQ0Lwk3nRXlZKPT9OiXl29oe6zSPD2YNaFpkyydYFYt8CXMO 9X/YXAeUOgHnYmIxNFevn/BxOWqgvQpHxR6ei6j9dI= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On my AMD780V chipset, hda_intel.c can crash the kernel with a divide by zero for as-yet unknown reasons. A simple check for zero prevents it, though the problem that causes it remains. Since the workaround is harmless and won't affect anyone except victims of this bug, it should be safe; moreover, because this crash can be triggered by a user-mode application, there are denial of service implications on the systems affected by the bug without the patch. Signed-off-by: Jody Bruchon --- linux-2.6.33-rc6/sound/pci/hda/hda_intel.c 2010-01-29 16:57:50.000000000 -0500 +++ linux-2.6.33-rc6-fix/sound/pci/hda/hda_intel.c 2010-02-06 09:44:10.028348166 -0500 @@ -1878,6 +1878,12 @@ if (!bdl_pos_adj[chip->dev_index]) return 1; /* no delayed ack */ + if (azx_dev->period_bytes == 0) { + printk(KERN_WARNING + "hda-intel: Divide by zero was avoided " + "in azx_dev->period_bytes.\n"); + return 0; + } if (pos % azx_dev->period_bytes > azx_dev->period_bytes / 2) return 0; /* NG - it's below the period boundary */ return 1; /* OK, it's fine */