nvme-pci: add missing condition check for existence of mapped data

[ Upstream commit c31fad1470 ]

nvme_map_data() is called when request has physical segments, hence
the nvme_unmap_data() should have same condition to avoid dereference.

Fixes: 4aedb70543 ("nvme-pci: split metadata handling from nvme_map_data / nvme_unmap_data")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/nvme/host/pci.c

@@ -938,7 +938,8 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
 	nvme_submit_cmd(nvmeq, &cmnd, bd->last);
 	return BLK_STS_OK;
 out_unmap_data:
-	nvme_unmap_data(dev, req);
+	if (blk_rq_nr_phys_segments(req))
+		nvme_unmap_data(dev, req);
 out_free_cmd:
 	nvme_cleanup_cmd(req);
 	return ret;