Re: [PATCH 1/2] libxfs: add more bounds checking to sb sanity checks

[Dave Chinner <david@fromorbit.com>]

On Thu, Jul 26, 2018 at 10:35:19AM -0700, Darrick J. Wong wrote:
> From: Bill O'Donnell <billodo@redhat.com>
> 
> Current sb verifier doesn't check bounds on sb_fdblocks and sb_ifree.
> Add sanity checks for these parameters.
> 
> Signed-off-by: Bill O'Donnell <billodo@redhat.com>
> [darrick: remove the icount check, tweak the comments a little]
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_sb.c |   45 +++++++++++++++++++++++++++++++++++----------
>  1 file changed, 35 insertions(+), 10 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> index b3ad15956366..b2c683588519 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -599,22 +599,16 @@ xfs_sb_to_disk(
>  static int
>  xfs_sb_verify(
>  	struct xfs_buf	*bp,
> +	struct xfs_sb	*sb,
>  	bool		check_version)
>  {
>  	struct xfs_mount *mp = bp->b_target->bt_mount;
> -	struct xfs_sb	sb;
> -
> -	/*
> -	 * Use call variant which doesn't convert quota flags from disk 
> -	 * format, because xfs_mount_validate_sb checks the on-disk flags.
> -	 */
> -	__xfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp), false);
>  
>  	/*
>  	 * Only check the in progress field for the primary superblock as
>  	 * mkfs.xfs doesn't clear it from secondary superblocks.
>  	 */
> -	return xfs_mount_validate_sb(mp, &sb,
> +	return xfs_mount_validate_sb(mp, sb,
>  				     bp->b_maps[0].bm_bn == XFS_SB_DADDR,
>  				     check_version);

Why do we need to keep this wrapper function? The in-progress check
is a primary superblock read verifier check (only useful at mount
time), as is the "check_version" flag used to validate the V5
feature mask during mount.

i.e. xfs_sb_verify() needs to go away, and the read-side only checks
need to be moved from xfs_mount_validate_sb() into
xfs_sb_read_verify() too. At which point, xfs_mount_validate_sb()
has nothing to do with mount and can be renamed to
xfs_sb_verify_common()....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com