linux-kernel - Re: [PATCH]Fix potential Divide by Zero error in ext2_get

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Message-Id: <20090513150425.89ac9b1c.akpm@linux-foundation.org>
Date:	Wed, 13 May 2009 15:04:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"B. N. Poornima" <poornima@...ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]Fix potential Divide by Zero error in ext2_get_inode()

On Wed, 13 May 2009 13:51:01 +0530
"B. N. Poornima" <poornima@...ibm.com> wrote:

> 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:

EXT2_INODES_PER_GROUP() cannot return zero.  See ext2_fill_super():

	if (sbi->s_inodes_per_block == 0 || sbi->s_inodes_per_group == 0)
		goto cantfind_ext2;

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