nbd: Aovid double completion of a request

There is a race between iterating over requests in
nbd_clear_que() and completing requests in recv_work(),
which can lead to double completion of a request.

To fix it, flush the recv worker before iterating over
the requests and don't abort the completed request
while iterating.

Fixes: 96d97e17828f ("nbd: clear_sock on netlink disconnect")
Reported-by: Jiang Yadong <jiangyadong@bytedance.com>
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210813151330.96-1-xieyongji@bytedance.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c38317979f74ec42a92885d7f963a49526bd8637..19f5d5a8b16a3cf7e57df67c50cf729d8b349b64 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -818,6 +818,10 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved)
 {
        struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
 
+       /* don't abort one completed request */
+       if (blk_mq_request_completed(req))
+               return true;
+
        mutex_lock(&cmd->lock);
        cmd->status = BLK_STS_IOERR;
        mutex_unlock(&cmd->lock);
@@ -2004,15 +2008,19 @@ static void nbd_disconnect_and_put(struct nbd_device *nbd)
 {
        mutex_lock(&nbd->config_lock);
        nbd_disconnect(nbd);
-       nbd_clear_sock(nbd);
-       mutex_unlock(&nbd->config_lock);
+       sock_shutdown(nbd);
        /*
         * Make sure recv thread has finished, so it does not drop the last
         * config ref and try to destroy the workqueue from inside the work
-        * queue.
+        * queue. And this also ensure that we can safely call nbd_clear_que()
+        * to cancel the inflight I/Os.
         */
        if (nbd->recv_workq)
                flush_workqueue(nbd->recv_workq);
+       nbd_clear_que(nbd);
+       nbd->task_setup = NULL;
+       mutex_unlock(&nbd->config_lock);
+
        if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF,
                               &nbd->config->runtime_flags))
                nbd_config_put(nbd);