linux-kernel - [PATCH AUTOSEL 5.8 26/29] nvme-pci: fix NULL req in completion handler

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Date:   Mon, 28 Sep 2020 21:30:23 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xianting Tian <tian.xianting@....com>,
        Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sasha Levin <sashal@...nel.org>, linux-nvme@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.8 26/29] nvme-pci: fix NULL req in completion handler

From: Xianting Tian <tian.xianting@....com>

[ Upstream commit 50b7c24390a53c78de546215282fb52980f1d7b7 ]

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: Xianting Tian <tian.xianting@....com>
Reviewed-by: Keith Busch <kbusch@...nel.org>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/nvme/host/pci.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 90346cba87d1e..cc3ae9c63a01b 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -942,13 +942,6 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 	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
@@ -962,6 +955,13 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 	}
 
 	req = blk_mq_tag_to_rq(nvme_queue_tagset(nvmeq), 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;
+	}
+
 	trace_nvme_sq(req, cqe->sq_head, nvmeq->sq_tail);
 	nvme_end_request(req, cqe->status, cqe->result);
 }
-- 
2.25.1