[PATCH] xfs: fix possible overflow in xfs_ioc_trim()

[Chandra Seetharaman]

On Mon, 2011-09-05 at 16:33 +0200, Lukas Czerner wrote:
> In xfs_ioc_trim it is possible that start+len might overflow. Fix it by
> decrementing the len so that start+len equals to the file system size in
> the worst case.
> 
> Signed-off-by: Lukas Czerner <lczerner at redhat.com>
> ---
>  fs/xfs/xfs_discard.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
> index 244e797..0fab107 100644
> --- a/fs/xfs/xfs_discard.c
> +++ b/fs/xfs/xfs_discard.c
> @@ -146,6 +146,7 @@ xfs_ioc_trim(
>  	unsigned int		granularity = q->limits.discard_granularity;
>  	struct fstrim_range	range;
>  	xfs_fsblock_t		start, len, minlen;
> +	xfs_fsblock_t		max_blks =  XFS_MAX_DBLOCKS(&(mp->m_sb));
>  	xfs_agnumber_t		start_agno, end_agno, agno;
>  	__uint64_t		blocks_trimmed = 0;
>  	int			error, last_error = 0;
> @@ -171,7 +172,8 @@ xfs_ioc_trim(
>  	start_agno = XFS_FSB_TO_AGNO(mp, start);
>  	if (start_agno >= mp->m_sb.sb_agcount)
>  		return -XFS_ERROR(EINVAL);
> -
> +	if (len > max_blks)

just wondering....

shouldn't this be ((start + len) > max_blks) ?

> +		len = max_blks - start;
>  	end_agno = XFS_FSB_TO_AGNO(mp, start + len);
>  	if (end_agno >= mp->m_sb.sb_agcount)
>  		end_agno = mp->m_sb.sb_agcount - 1;