From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758433AbZEMIVg (ORCPT ); Wed, 13 May 2009 04:21:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758178AbZEMIVF (ORCPT ); Wed, 13 May 2009 04:21:05 -0400 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:53835 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758149AbZEMIVB (ORCPT ); Wed, 13 May 2009 04:21:01 -0400 Message-ID: <4A0A82ED.2040906@in.ibm.com> Date: Wed, 13 May 2009 13:51:01 +0530 From: "B. N. Poornima" User-Agent: Thunderbird 2.0.0.21 (X11/20090302) MIME-Version: 1.0 To: linux-kernel Subject: [PATCH]Fix potential Divide by Zero error in ext2_get_inode() Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Found a line of code in ext2_get_inode function of inode.c in the ext2 filesystem that has the potential of hitting the divide by 0 error. ************************************************* block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb); ************************************************* There is no checking done here to verify if EXT2_INODES_PER_GROUP() returns 0. This could result in divide by zero error and panic the system. Below is the patch, built against 2.6.30-rc5, to correct the same: Signed-off-by: B N Poornima Index: linux-2.6.30-rc5/fs/ext2/inode.c =================================================================== --- linux-2.6.30-rc5.orig/fs/ext2/inode.c 2009-05-09 05:44:14.000000000 +0530 +++ linux-2.6.30-rc5/fs/ext2/inode.c 2009-05-12 19:14:42.873991280 +0530 @@ -1138,6 +1138,7 @@ unsigned long block_group; unsigned long block; unsigned long offset; + unsigned long inodes_per_group; struct ext2_group_desc * gdp; *p = NULL; @@ -1145,7 +1146,10 @@ ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count)) goto Einval; - block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb); + inodes_per_group = EXT2_INODES_PER_GROUP(sb); + if (!inodes_per_group) + goto Einval1; + block_group = (ino - 1) / inodes_per_group; gdp = ext2_get_group_desc(sb, block_group, NULL); if (!gdp) goto Egdp; @@ -1166,6 +1170,11 @@ ext2_error(sb, "ext2_get_inode", "bad inode number: %lu", (unsigned long) ino); return ERR_PTR(-EINVAL); + +Einval1: + printk(KERN_ERR "Ext2-fs: Filesystem corrupted. Wrong inodes per group: %lu, run e2fsck\n", (unsigned long)inodes_per_group); + return ERR_PTR(-EINVAL); + Eio: ext2_error(sb, "ext2_get_inode", "unable to read inode block - inode=%lu, block=%lu",