Messages in this thread Patch in this message |  | | | Date | Wed, 13 May 2009 13:51:01 +0530 | | From | "B. N. Poornima" <> | | Subject | [PATCH]Fix potential Divide by Zero error in ext2_get_inode() |
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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 <poornima@in.ibm.com>
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",
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