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 <[email protected]>
> Cc: [email protected]
>
> ---
> 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 <[email protected]>
--
Damien Le Moal
Western Digital Research
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