[PATCH 2/3] iommu/dma: Use correct offset in map_sg

[joro@8bytes.org (Joerg Roedel)]

On Fri, Dec 18, 2015 at 05:01:47PM +0000, Robin Murphy wrote:
> When mapping a non-page-aligned scatterlist entry, we copy the original
> offset to the output DMA address before aligning it to hand off to
> iommu_map_sg(), then later adding the IOVA page address portion to get
> the final mapped address. However, when the IOVA page size is smaller
> than the CPU page size, it is the offset within the IOVA page we want,
> not that within the CPU page, which can easily be larger than an IOVA
> page and thus result in an incorrect final address.
> 
> Fix the bug by taking only the IOVA-aligned part of the offset as the
> basis of the DMA address, not the whole thing.
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.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 982e716..03811e3 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -458,7 +458,7 @@ int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
>  		size_t s_length = s->length;
>  		size_t pad_len = (mask - iova_len + 1) & mask;
>  
> -		sg_dma_address(s) = s->offset;
> +		sg_dma_address(s) = s_offset;

Does not apply on v4.4-rc7.