nvme-pci: fix NULL req in completion handler

mainline inclusion
from mainline-5.9-rc7
commit 50b7c243
category: bugfix
bugzilla: 167363
CVE: NA

---------------------------

Currently, we use nvmeq->q_depth as the upper limit for a valid tag in
nvme_handle_cqe(), it is not correct. Because the available tag number
is recorded in tagset, which is not equal to nvmeq->q_depth.

The nvme driver registers interrupts for queues before initializing the
tagset, because it uses the number of successful request_irq() calls to
configure the tagset parameters. This allows a race condition with the
current tag validity check if the controller happens to produce an
interrupt with a corrupted CQE before the tagset is initialized.

Replace the driver's indirect tag check with the one already provided by
the block layer.
Signed-off-by: NXianting Tian <tian.xianting@h3c.com>
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Conflicts:
	drivers/nvme/host/pci.c
	[ Cleanup commit cfa27356 ("nvme-pci: remove nvmeq->tags")
	  is not applied. ]
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/nvme/host/pci.c

@@ -889,13 +889,6 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 	volatile struct nvme_completion *cqe = &nvmeq->cqes[idx];
 	struct request *req;
 
-	if (unlikely(cqe->command_id >= nvmeq->q_depth)) {
-		dev_warn(nvmeq->dev->ctrl.device,
-			"invalid id %d completed on queue %d\n",
-			cqe->command_id, le16_to_cpu(cqe->sq_id));
-		return;
-	}
-
 	/*
 	 * AEN requests are special as they don't time out and can
 	 * survive any kind of queue freeze and often don't respond to
@@ -910,6 +903,13 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 	}
 
 	req = blk_mq_tag_to_rq(*nvmeq->tags, cqe->command_id);
+	if (unlikely(!req)) {
+		dev_warn(nvmeq->dev->ctrl.device,
+			"invalid id %d completed on queue %d\n",
+			cqe->command_id, le16_to_cpu(cqe->sq_id));
+		return;
+	}
+
 	nvme_end_request(req, cqe->status, cqe->result);
 }