On Thu, Sep 09, 2021 at 10:12:55PM +0800, Yu Kuai wrote: > blk_mq_tag_to_rq() can only ensure to return valid request in > following situation: > > 1) client send request message to server first > submit_bio > ... > blk_mq_get_tag > ... > blk_mq_get_driver_tag > ... > nbd_queue_rq > nbd_handle_cmd > nbd_send_cmd > > 2) client receive respond message from server > recv_work > nbd_read_stat > blk_mq_tag_to_rq > > If step 1) is missing, blk_mq_tag_to_rq() will return a stale > request, which might be freed. Thus convert to use > blk_mq_find_and_get_req() to make sure the returned request is not > freed. But NBD_CMD_INFLIGHT has been added for checking if the reply is expected, do we still need blk_mq_find_and_get_req() for covering this issue? BTW, request and its payload is pre-allocated, so there isn't real use-after-free. Thanks, Ming
