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