Re: [PATCH] Avoid disk sector_t overflow for >2TB ext3 filesystem

On May 22, 2006  11:24 -0700, Mingming Cao wrote:
> If ext3 filesystem is larger than 2TB, and sector_t is a u32 (i.e.
> CONFIG_LBD not defined in the kernel), the calculation of the disk
> sector will overflow. Add check at ext3_fill_super() and
> ext3_group_extend() to prevent mount/remount/resize >2TB ext3 filesystem
> if sector_t size is 4 bytes.
> 
> Verified this patch on a 32 bit platform without CONFIG_LBD defined
> (sector_t is 32 bits long), mount refuse to mount a 10TB ext3. Patch
> against 2.6.17-rc4.
> 
> Signed-Off-By: Mingming Cao<[email protected]>
> 
> 
> ---
> 
>  linux-2.6.16-ming/fs/ext3/resize.c |    9 +++++++++
>  linux-2.6.16-ming/fs/ext3/super.c  |   10 ++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff -puN fs/ext3/super.c~ext3_check_sector_t_overflow fs/ext3/super.c
> --- linux-2.6.16/fs/ext3/super.c~ext3_check_sector_t_overflow	2006-05-19 17:19:43.000000000 -0700
> +++ linux-2.6.16-ming/fs/ext3/super.c	2006-05-22 10:54:27.000000000 -0700
> @@ -1579,6 +1579,16 @@ static int ext3_fill_super (struct super
>  		goto failed_mount;
>  	}
>  
> +	if (le32_to_cpu(es->s_blocks_count) >
> +		(sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
> +		printk(KERN_ERR "EXT3-fs: filesystem on %s"
> +			" too large to mount safely\n", sb->s_id);

Minor - it's a bit easier to read the code if the "continuation" line is
left-justified with the parenthesis instead of the tab on the next line.
It would also be nice to print out the actual values involved:

	if (le32_to_cpu(es->s_blocks_count) >
	    (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
		printk(KERN_ERR "EXT3-fs: filesystem on %s (%lu blocks) "
		       "too large to mount safely\n", sb->s_id,
		       le32_to_cpu(es->s_blocks_count));

> @@ -926,6 +926,15 @@ int ext3_group_extend(struct super_block
>  	if (n_blocks_count == 0 || n_blocks_count == o_blocks_count)
>  		return 0;
>  
> +	if (n_blocks_count > (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
> +		printk(KERN_ERR "EXT3-fs: filesystem on %s"
> +			" too large to mount safely\n", sb->s_id);

Minor - "too large to resize to %lu blocks safely\n", sb->s_id, n_blocks_count

You can add an:
Signed-Off-By: Andreas Dilger <[email protected]>

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.



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