Re: [PATCH 1/2] xfs: limit entries returned when counting fsmap records

[Chandan Babu R <chandanrlinux@gmail.com>]

On Friday 2 October 2020 10:19:24 AM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> If userspace asked fsmap to count the number of entries, we cannot
> return more than UINT_MAX entries because fmh_entries is u32.
> Therefore, stop counting if we hit this limit or else we will waste time
> to return truncated results.
> 
> Fixes: e89c041338ed ("xfs: implement the GETFSMAP ioctl")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

The upper bound check is correct.

Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

> ---
>  fs/xfs/xfs_fsmap.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> 
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> index 4eebcec4aae6..aa36e7daf82c 100644
> --- a/fs/xfs/xfs_fsmap.c
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -256,6 +256,9 @@ xfs_getfsmap_helper(
>  
>  	/* Are we just counting mappings? */
>  	if (info->head->fmh_count == 0) {
> +		if (info->head->fmh_entries == UINT_MAX)
> +			return -ECANCELED;
> +
>  		if (rec_daddr > info->next_daddr)
>  			info->head->fmh_entries++;
>  
> 
> 


-- 
chandan