linux-kernel - [PATCH] nvme: pci: Use the same attributes when freeing host_mem_desc

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Date:   Sat, 29 Dec 2018 17:23:43 +0000
From:   Liviu Dudau <liviu@...au.co.uk>
To:     Keith Busch <keith.busch@...el.com>
Cc:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Liviu Dudau <liviu@...au.co.uk>
Subject: [PATCH] nvme: pci: Use the same attributes when freeing host_mem_desc_bufs.

When using HMB the PCIe host driver allocates host_mem_desc_bufs using
dma_alloc_attrs() but frees them using dma_free_coherent(). Use the
correct dma_free_attrs() function to free the buffers.

Found out while doing some code inspection to figure out broken
NVMe support in linux-next-20181224. Without this change I'm getting
a kernel crash due to an invalid VM area being freed.

Signed-off-by: Liviu Dudau <liviu@...au.co.uk>
---
 drivers/nvme/host/pci.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index c33bb201b8846..0f45868e8af98 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1748,8 +1748,9 @@ static void nvme_free_host_mem(struct nvme_dev *dev)
 		struct nvme_host_mem_buf_desc *desc = &dev->host_mem_descs[i];
 		size_t size = le32_to_cpu(desc->size) * dev->ctrl.page_size;
 
-		dma_free_coherent(dev->dev, size, dev->host_mem_desc_bufs[i],
-				le64_to_cpu(desc->addr));
+		dma_free_attrs(dev->dev, size, dev->host_mem_desc_bufs[i],
+			       le64_to_cpu(desc->addr),
+			       DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_NO_WARN);
 	}
 
 	kfree(dev->host_mem_desc_bufs);
@@ -1815,8 +1816,9 @@ static int __nvme_alloc_host_mem(struct nvme_dev *dev, u64 preferred,
 	while (--i >= 0) {
 		size_t size = le32_to_cpu(descs[i].size) * dev->ctrl.page_size;
 
-		dma_free_coherent(dev->dev, size, bufs[i],
-				le64_to_cpu(descs[i].addr));
+		dma_free_attrs(dev->dev, size, bufs[i],
+			       le64_to_cpu(descs[i].addr),
+			       DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_NO_WARN);
 	}
 
 	kfree(bufs);
-- 
2.20.1