Re: [PATCH 3/5] ext4: Extent overlap bugfix

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

On Thu, 26 Apr 2007 23:41:01 +0530 "Amit K. Arora" <aarora@xxxxxxxxxxxxxxxxxx> 
wrote:

> +unsigned int ext4_ext_check_overlap(struct inode *inode,
> +                                     struct ext4_extent *newext,
> +                                     struct ext4_ext_path *path)
> +{
> +     unsigned long b1, b2;
> +     unsigned int depth, len1;
> +
> +     b1 = le32_to_cpu(newext->ee_block);
> +     len1 = le16_to_cpu(newext->ee_len);
> +     depth = ext_depth(inode);
> +     if (!path[depth].p_ext)
> +             goto out;
> +     b2 = le32_to_cpu(path[depth].p_ext->ee_block);
> +
> +     /* get the next allocated block if the extent in the path
> +      * is before the requested block(s) */
> +     if (b2 < b1) {
> +             b2 = ext4_ext_next_allocated_block(path);
> +             if (b2 == EXT_MAX_BLOCK)
> +                     goto out;
> +     }
> +
> +     if (b1 + len1 > b2) {

Are we sure that b1+len cannot wrap through zero here?

> +             newext->ee_len = cpu_to_le16(b2 - b1);
> +             return 1;
> +     }