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From: chenxiang <chenxiang66@hisilicon.com>
To: <robin.murphy@arm.com>, <will@kernel.org>, <joro@8bytes.org>,
	<hch@lst.de>
Cc: iommu@lists.linux-foundation.org, linuxarm@openeuler.org,
	linuxarm@huawei.com
Subject: [PATCH] dma-iommu: Add a check to avoid dereference null pointer in function iommu_dma_map_sg()
Date: Fri, 21 May 2021 11:05:34 +0800	[thread overview]
Message-ID: <1621566334-93468-1-git-send-email-chenxiang66@hisilicon.com> (raw)

From: Xiang Chen <chenxiang66@hisilicon.com>

The issue is reported by tool TscanCode, and it is possible to deference
null pointer when prev is NULL which is the initial value.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
---
 drivers/iommu/dma-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 4cb63b2..88a4f34 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1042,7 +1042,7 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
 		 *   iova_len == 0, thus we cannot dereference prev the first
 		 *   time through here (i.e. before it has a meaningful value).
 		 */
-		if (pad_len && pad_len < s_length - 1) {
+		if (prev && pad_len && pad_len < s_length - 1) {
 			prev->length += pad_len;
 			iova_len += pad_len;
 		}
-- 
2.8.1

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             reply	other threads:[~2021-05-21  3:09 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-21  3:05 chenxiang [this message]
2021-05-21 10:36 ` [PATCH] dma-iommu: Add a check to avoid dereference null pointer in function iommu_dma_map_sg() Robin Murphy
2021-05-21 12:34   ` chenxiang (M)

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