From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756676Ab0C3XNJ (ORCPT ); Tue, 30 Mar 2010 19:13:09 -0400 Received: from kroah.org ([198.145.64.141]:49170 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756613Ab0C3XMv (ORCPT ); Tue, 30 Mar 2010 19:12:51 -0400 X-Mailbox-Line: From linux@linux.site Tue Mar 30 15:58:49 2010 Message-Id: <20100330225848.836048640@linux.site> User-Agent: quilt/0.47-14.9 Date: Tue, 30 Mar 2010 15:58:07 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jody Bruchon , Takashi Iwai , Greg Kroah-Hartman Subject: [65/89] ALSA: hda-intel: Avoid divide by zero crash In-Reply-To: <20100330230520.GA28779@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.31-stable review patch. If anyone has any objections, please let us know. ------------------ From: Jody Bruchon commit fed08d036f2aabd8d0c684439de37f8ebec2bbc2 upstream. 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 Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/pci/hda/hda_intel.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/sound/pci/hda/hda_intel.c +++ b/sound/pci/hda/hda_intel.c @@ -1839,6 +1839,12 @@ static int azx_position_ok(struct azx *c 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 */