[dm-devel] [PATCH] dm: make sure dm_table is binded before queue request

[Zhang Yi]

Friendly ping.

On 2022/2/9 17:37, Zhang Yi wrote:
> We found a NULL pointer dereference problem when using dm-mpath target.
> The problem is if we submit IO between loading and binding the table,
> we could neither get a valid dm_target nor a valid dm table when
> submitting request in dm_mq_queue_rq(). BIO based dm target could
> handle this case in dm_submit_bio(). This patch fix this by checking
> the mapping table before submitting request.
> 
> Signed-off-by: Zhang Yi <yi.zhang at huawei.com>
> ---
>  drivers/md/dm-rq.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> index 579ab6183d4d..af2cf71519e9 100644
> --- a/drivers/md/dm-rq.c
> +++ b/drivers/md/dm-rq.c
> @@ -499,8 +499,15 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
>  
>  	if (unlikely(!ti)) {
>  		int srcu_idx;
> -		struct dm_table *map = dm_get_live_table(md, &srcu_idx);
> -
> +		struct dm_table *map;
> +
> +		map = dm_get_live_table(md, &srcu_idx);
> +		if (!map) {
> +			DMERR_LIMIT("%s: mapping table unavailable, erroring io",
> +				    dm_device_name(md));
> +			dm_put_live_table(md, srcu_idx);
> +			return BLK_STS_IOERR;
> +		}
>  		ti = dm_table_find_target(map, 0);
>  		dm_put_live_table(md, srcu_idx);
>  	}
>