[PATCH] arm: dma-mapping: fix off-by-one error in bitmap size check

[Ard Biesheuvel]

On 1 July 2015 at 14:48, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> nr_bitmaps member of mapping structure stores the number of already
> allocated bitmaps and it is interpreted as loop iterator (it starts from
> 0 not from 1), so a comparison against number of possible bitmap
> extensions should include this fact. This patch fixes this by changing
> the extension failure condition. This issue has been introduced by
> commit 4d852ef8c2544ce21ae41414099a7504c61164a0 ("arm: dma-mapping: Add
> support to extend DMA IOMMU mappings").
>
> Reported-by: Hyungwon Hwang <human.hwang at samsung.com>
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> CC: stable at vger.kernel.org  # v3.15+
> ---
>  arch/arm/mm/dma-mapping.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index a64b7f621067..05619542a1c0 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2015,7 +2015,7 @@ static int extend_iommu_mapping(struct dma_iommu_mapping *mapping)
>  {
>         int next_bitmap;
>
> -       if (mapping->nr_bitmaps > mapping->extensions)
> +       if (mapping->nr_bitmaps => mapping->extensions)

Did you build test this?

>                 return -EINVAL;
>
>         next_bitmap = mapping->nr_bitmaps;
> --
> 1.9.2
>
>
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