Re: [PATCH] xfs: check that dir block entries don't off the end of the buffer

[Brian Foster <bfoster@redhat.com>]

On Fri, Jul 21, 2017 at 03:01:22PM -0700, Darrick J. Wong wrote:
> When we're checking the entries in a directory buffer, make sure that
> the entry length doesn't push us off the end of the buffer.  Found via
> xfs/388 writing ones to the freetag length field and xfs_repair crashing.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_dir2_data.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
> index d478065..8727a43 100644
> --- a/fs/xfs/libxfs/xfs_dir2_data.c
> +++ b/fs/xfs/libxfs/xfs_dir2_data.c
> @@ -136,6 +136,8 @@ __xfs_dir3_data_check(
>  		 */
>  		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
>  			XFS_WANT_CORRUPTED_RETURN(mp, lastfree == 0);
> +			XFS_WANT_CORRUPTED_RETURN(mp, endp >=
> +					p + be16_to_cpu(dup->length));

FWIW, the rest of the code seems to use the dup/dep pointers for
verification and explicitly casts to char * where necessary. I don't see
that it really matters, so:

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  			XFS_WANT_CORRUPTED_RETURN(mp,
>  				be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)) ==
>  					       (char *)dup - (char *)hdr);
> @@ -164,6 +166,8 @@ __xfs_dir3_data_check(
>  		XFS_WANT_CORRUPTED_RETURN(mp, dep->namelen != 0);
>  		XFS_WANT_CORRUPTED_RETURN(mp,
>  			!xfs_dir_ino_validate(mp, be64_to_cpu(dep->inumber)));
> +		XFS_WANT_CORRUPTED_RETURN(mp, endp >=
> +				p + ops->data_entsize(dep->namelen));
>  		XFS_WANT_CORRUPTED_RETURN(mp,
>  			be16_to_cpu(*ops->data_entry_tag_p(dep)) ==
>  					       (char *)dep - (char *)hdr);
> --
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