Re: [PATCH] iommu/dma: Fix iova map result check bug

[Yong Wu via iommu <iommu@lists.linux-foundation.org>]

On Sat, 2022-05-07 at 16:52 +0800, yf.wang@mediatek.com wrote:
> From: Yunfei Wang <yf.wang@mediatek.com>
> 
> The data type of the return value of the iommu_map_sg_atomic
> is ssize_t, but the data type of iova size is size_t,
> e.g. one is int while the other is unsigned int.
> 
> When iommu_map_sg_atomic return value is compared with iova size,
> it will force the signed int to be converted to unsigned int, if
> iova map fails and iommu_map_sg_atomic return error code is less
> than 0, then (ret < iova_len) is false, which will to cause not
> do free iova, and the master can still successfully get the iova
> of map fail, which is not expected.
> 
> Therefore, we need to check the return value of iommu_map_sg_atomic
> in two cases according to whether it is less than 0.
> 
> Fixes: ad8f36e4b6b1 ("iommu: return full error code from
> iommu_map_sg[_atomic]()")
> Signed-off-by: Yunfei Wang <yf.wang@mediatek.com>
> Cc: <stable@vger.kernel.org> # 5.15.*
> ---
>  drivers/iommu/dma-iommu.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 09f6e1c0f9c0..2932281e93fc 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -776,6 +776,7 @@ static struct page
> **__iommu_dma_alloc_noncontiguous(struct device *dev,
>  	unsigned int count, min_size, alloc_sizes = domain-
> >pgsize_bitmap;
>  	struct page **pages;
>  	dma_addr_t iova;
> +	ssize_t ret;
>  
>  	if (static_branch_unlikely(&iommu_deferred_attach_enabled) &&
>  	    iommu_deferred_attach(dev, domain))
> @@ -813,8 +814,8 @@ static struct page
> **__iommu_dma_alloc_noncontiguous(struct device *dev,
>  			arch_dma_prep_coherent(sg_page(sg), sg-
> >length);
>  	}
>  
> -	if (iommu_map_sg_atomic(domain, iova, sgt->sgl, sgt-
> >orig_nents, ioprot)
> -			< size)
> +	ret = iommu_map_sg_atomic(domain, iova, sgt->sgl, sgt-
> >orig_nents, ioprot);
> +	if (ret < 0 || ret < size)

        if (IS_ERR_VALUE(ret) || ret < size) for readable?

>  		goto out_free_sg;
>  
>  	sgt->sgl->dma_address = iova;
> @@ -1209,7 +1210,7 @@ static int iommu_dma_map_sg(struct device *dev,
> struct scatterlist *sg,
>  	 * implementation - it knows better than we do.
>  	 */
>  	ret = iommu_map_sg_atomic(domain, iova, sg, nents, prot);
> -	if (ret < iova_len)
> +	if (ret < 0 || ret < iova_len)
>  		goto out_free_iova;
>  
>  	return __finalise_sg(dev, sg, nents, iova);

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