Re: [PATCH 07/10] xfs: xfs_alloc_get_rec should return EFSCORRUPTED for obvious bnobt corruption

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Jun 04, 2018 at 10:14:06AM +1000, Dave Chinner wrote:
> On Sun, Jun 03, 2018 at 04:23:08PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Return -EFSCORRUPTED when the bnobt/cntbt return obviously corrupt
> > values, rather than letting them bounce around in the internal code.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/libxfs/xfs_alloc.c |   12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > index dc9dd3805d97..0214a77808d0 100644
> > --- a/fs/xfs/libxfs/xfs_alloc.c
> > +++ b/fs/xfs/libxfs/xfs_alloc.c
> > @@ -231,10 +231,14 @@ xfs_alloc_get_rec(
> >  	int			error;
> >  
> >  	error = xfs_btree_get_rec(cur, &rec, stat);
> > -	if (!error && *stat == 1) {
> > -		*bno = be32_to_cpu(rec->alloc.ar_startblock);
> > -		*len = be32_to_cpu(rec->alloc.ar_blockcount);
> > -	}
> > +	if (error || !(*stat))
> > +		return error;
> > +	if (rec->alloc.ar_blockcount == 0)
> > +		return -EFSCORRUPTED;
> > +
> > +	*bno = be32_to_cpu(rec->alloc.ar_startblock);
> > +	*len = be32_to_cpu(rec->alloc.ar_blockcount);
> 
> Looks good, but makes me wonder if we should verify that
> ar_startblock is a valid agbno, and that the extent lies wholly
> within the AG? That can be another patch, though.

We probably ought to fix all the _get_rec functions to check that
they're not returning obviously garbage results.

--D

> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> 
> Cheers,
> 
> Dave.
> 
> -- 
> Dave Chinner
> david@fromorbit.com
> --
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