nvme-rdma: fix a NULL deref when an admin connect times out

If we timeout the admin startup sequence we might not yet have
an I/O tagset allocated which causes the teardown sequence to crash.
Make nvme_tcp_teardown_io_queues safe by not iterating inflight tags
if the tagset wasn't allocated.

Fixes: 4c174e63 ("nvme-rdma: fix timeout handler")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/rdma.c

@@ -914,8 +914,9 @@ static void nvme_rdma_teardown_admin_queue(struct nvme_rdma_ctrl *ctrl,
 {
 	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
 	nvme_rdma_stop_queue(&ctrl->queues[0]);
-	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set, nvme_cancel_request,
-			&ctrl->ctrl);
+	if (ctrl->ctrl.admin_tagset)
+		blk_mq_tagset_busy_iter(ctrl->ctrl.admin_tagset,
+			nvme_cancel_request, &ctrl->ctrl);
 	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 	nvme_rdma_destroy_admin_queue(ctrl, remove);
 }
@@ -926,8 +927,9 @@ static void nvme_rdma_teardown_io_queues(struct nvme_rdma_ctrl *ctrl,
 	if (ctrl->ctrl.queue_count > 1) {
 		nvme_stop_queues(&ctrl->ctrl);
 		nvme_rdma_stop_io_queues(ctrl);
-		blk_mq_tagset_busy_iter(&ctrl->tag_set, nvme_cancel_request,
-				&ctrl->ctrl);
+		if (ctrl->ctrl.tagset)
+			blk_mq_tagset_busy_iter(ctrl->ctrl.tagset,
+				nvme_cancel_request, &ctrl->ctrl);
 		if (remove)
 			nvme_start_queues(&ctrl->ctrl);
 		nvme_rdma_destroy_io_queues(ctrl, remove);