linux-ext4 - Re: [RFC PATCH 11/17] Fix overflow in calculation of total file system blocks

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Date:	Thu, 13 Nov 2008 13:04:02 -0700
From:	Andreas Dilger <adilger@....com>
To:	Valerie Aurora Henson <vaurora@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [RFC PATCH 11/17] Fix overflow in calculation of total file	system
 blocks

On Nov 11, 2008  19:43 -0800, Valerie Aurora Henson wrote:
> Blocks per group and group desc count are both 32-bit; multiplied they
> produce a 32-bit quantity which overflowed.
> 
> @@ -92,8 +92,8 @@ errcode_t ext2fs_allocate_block_bitmap(ext2_filsys fs,
> -	real_end = (EXT2_BLOCKS_PER_GROUP(fs->super)
> -		    * fs->group_desc_count)-1 + start;
> +	real_end = ((__u64) EXT2_BLOCKS_PER_GROUP(fs->super)
> +		    * (__u64) fs->group_desc_count)-1 + start;

Casting the first value to __u64 should be enough.

This should really be part of patch 05/17 because that is where "real_end"
is turned into a 64-bit value.

There is a similar fix missing from ext2fs_allocate_inode_bitmap() (even
though there isn't any support for 64-bit inode numbers as yet.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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