nbd: make sure request completion won't concurrent
mainline inclusion from mainline-next-20211018 commit d14b304f558f8c8f53da3a8d0c0b671f14a9c2f4 category: bugfix bugzilla: 49890 CVE: NA --------------------------- commit cddce0116058 ("nbd: Aovid double completion of a request") try to fix that nbd_clear_que() and recv_work() can complete a request concurrently. However, the problem still exists: t1 t2 t3 nbd_disconnect_and_put flush_workqueue recv_work blk_mq_complete_request blk_mq_complete_request_remote -> this is true WRITE_ONCE(rq->state, MQ_RQ_COMPLETE) blk_mq_raise_softirq blk_done_softirq blk_complete_reqs nbd_complete_rq blk_mq_end_request blk_mq_free_request WRITE_ONCE(rq->state, MQ_RQ_IDLE) nbd_clear_que blk_mq_tagset_busy_iter nbd_clear_req __blk_mq_free_request blk_mq_put_tag blk_mq_complete_request -> complete again There are three places where request can be completed in nbd: recv_work(), nbd_clear_que() and nbd_xmit_timeout(). Since they all hold cmd->lock before completing the request, it's easy to avoid the problem by setting and checking a cmd flag. Signed-off-by:Yu Kuai <yukuai3@huawei.com> Reviewed-by:
Ming Lei <ming.lei@redhat.com> Reviewed-by:
Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20210916093350.1410403-3-yukuai3@huawei.com Signed-off-by:
Jens Axboe <axboe@kernel.dk> Conflict: drivers/block/nbd.c Signed-off-by:
Yu Kuai <yukuai3@huawei.com> Reviewed-by:
Jason Yan <yanaijie@huawei.com> Signed-off-by:
Yang Yingliang <yangyingliang@huawei.com>
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