[dm-devel] [PATCH] accessing invalid memory in "dm zoned: properly handle backing device failure"

[Mikulas Patocka]

On Mon, 26 Aug 2019, Damien Le Moal wrote:

> On 2019/08/26 15:41, Mikulas Patocka wrote:
> > The patch 75d66ffb48efb30f2dd42f041ba8b39c5b2bd115 ("dm zoned: properly 
> > handle backing device failure") triggers a coverity warning:
> > 
> > *** CID 1452808:  Memory - illegal accesses  (USE_AFTER_FREE)
> > /drivers/md/dm-zoned-target.c: 137 in dmz_submit_bio()
> > 131             clone->bi_private = bioctx;
> > 132
> > 133             bio_advance(bio, clone->bi_iter.bi_size);
> > 134
> > 135             refcount_inc(&bioctx->ref);
> > 136             generic_make_request(clone);
> >>>>     CID 1452808:  Memory - illegal accesses  (USE_AFTER_FREE)
> >>>>     Dereferencing freed pointer "clone".
> > 137             if (clone->bi_status == BLK_STS_IOERR)
> > 138                     return -EIO;
> > 139
> > 140             if (bio_op(bio) == REQ_OP_WRITE && dmz_is_seq(zone))
> > 141                     zone->wp_block += nr_blocks;
> > 142
> > 
> > The "clone" bio may be processed and freed before the check 
> > "clone->bi_status == BLK_STS_IOERR" - so this check can access invalid 
> > memory.
> > 
> > Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> > Cc: stable at vger.kernel.org

We should also append this line:

Fixes: 75d66ffb48ef ("dm zoned: properly handle backing device failure")

Mikulas

> > ---
> >  drivers/md/dm-zoned-target.c |    2 --
> >  1 file changed, 2 deletions(-)
> > 
> > Index: linux-2.6/drivers/md/dm-zoned-target.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/md/dm-zoned-target.c	2019-08-26 08:30:30.000000000 +0200
> > +++ linux-2.6/drivers/md/dm-zoned-target.c	2019-08-26 08:36:23.000000000 +0200
> > @@ -134,8 +134,6 @@ static int dmz_submit_bio(struct dmz_tar
> >  
> >  	refcount_inc(&bioctx->ref);
> >  	generic_make_request(clone);
> > -	if (clone->bi_status == BLK_STS_IOERR)
> > -		return -EIO;
> >  
> >  	if (bio_op(bio) == REQ_OP_WRITE && dmz_is_seq(zone))
> >  		zone->wp_block += nr_blocks;
> > 
> 
> Argh... Indeed. Thanks Mikulas.
> 
> Reviewed-by: Damien Le Moal <damien.lemoal at wdc.com>
> 
> -- 
> Damien Le Moal
> Western Digital Research
>