Re: [PATCH v2] ext4: avoid eh_entries overflow before insert extent_idx

[Eric Sandeen <sandeen@redhat.com>]

On 6/23/11 3:47 AM, Robin Dong wrote:
> If eh_entries is equal to (or greater than) eh_max, the operation of
> inserting new extent_idx will make number of entries overflow.
> So check eh_entries before inserting the new extent_idx.

Do you have any testcase you can share which shows this bug?

Thanks,
-Eric

> Signed-off-by: Robin Dong <sanbai@taobao.com>
> ---
>  fs/ext4/extents.c |   18 ++++++++++--------
>  1 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index eb63c7b..792e77e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -776,6 +776,16 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
>  				 logical, le32_to_cpu(curp->p_idx->ei_block));
>  		return -EIO;
>  	}
> +
> +	if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
> +			     >= le16_to_cpu(curp->p_hdr->eh_max))) {
> +		EXT4_ERROR_INODE(inode,
> +				 "eh_entries %d >= eh_max %d!",
> +				 le16_to_cpu(curp->p_hdr->eh_entries),
> +				 le16_to_cpu(curp->p_hdr->eh_max));
> +		return -EIO;
> +	}
> +
>  	len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
>  	if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
>  		/* insert after */
> @@ -805,14 +815,6 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
>  	ext4_idx_store_pblock(ix, ptr);
>  	le16_add_cpu(&curp->p_hdr->eh_entries, 1);
>  
> -	if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
> -			     > le16_to_cpu(curp->p_hdr->eh_max))) {
> -		EXT4_ERROR_INODE(inode,
> -				 "eh_entries %d > eh_max %d!",
> -				 le16_to_cpu(curp->p_hdr->eh_entries),
> -				 le16_to_cpu(curp->p_hdr->eh_max));
> -		return -EIO;
> -	}
>  	if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
>  		EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
>  		return -EIO;