[PATCH] arm: dma-mapping: fix off-by-one check in arm_setup_iommu_dma_ops
Robin Murphy
robin.murphy at arm.com
Tue Apr 28 07:52:24 PDT 2015
Hi Marek,
On 28/04/15 10:08, Marek Szyprowski wrote:
> Patch 22b3c181c6c324a46f71aae806d8ddbe61d25761 ("arm: dma-mapping: limit
> IOMMU mapping size") added a check for IO address space size. However
> this patch broke IOMMU initialization for typical platforms initialized
> from device tree, which get the default IO address space size of 4GiB.
> This value doesn't fit into size_t and fails a check introduced by that
> commit resulting in failed dma-mapping/iommu initialization. This patch
> fixes this issue by adding proper support for full 4GiB address space
> size.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
Much nicer than my hack of just passing in size-1, thanks! I'd offer a
tested-by for the default 32-bit case, however...
> ---
> arch/arm/include/asm/dma-iommu.h | 2 +-
> arch/arm/mm/dma-mapping.c | 9 +++------
> 2 files changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h
> index 8e3fcb924db6..2ef282f96651 100644
> --- a/arch/arm/include/asm/dma-iommu.h
> +++ b/arch/arm/include/asm/dma-iommu.h
> @@ -25,7 +25,7 @@ struct dma_iommu_mapping {
> };
>
> struct dma_iommu_mapping *
> -arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size);
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size);
>
> void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping);
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 09c5fe3d30c2..b43b762eebc1 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1878,7 +1878,7 @@ struct dma_map_ops iommu_coherent_ops = {
> * arm_iommu_attach_device function.
> */
> struct dma_iommu_mapping *
> -arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size)
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size)
> {
> unsigned int bits = size >> PAGE_SHIFT;
...doesn't this u64->int conversion now have the potential to truncate
(if the device has a large enough DMA mask specified) and end up
generating a weirdly small mapping rather than failing outright?
Admittedly you'd have to have a 44-bit or larger DMA mask, and I'm not
sure what the practical likelihood of seeing that even on LPAE systems
is, but still I'm a little uneasy about it.
Robin.
> unsigned int bitmap_size = BITS_TO_LONGS(bits) * sizeof(long);
> @@ -2057,11 +2057,8 @@ static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
> if (!iommu)
> return false;
>
> - /*
> - * currently arm_iommu_create_mapping() takes a max of size_t
> - * for size param. So check this limit for now.
> - */
> - if (size > SIZE_MAX)
> + /* Only 32-bit DMA address space is supported for now */
> + if (size > DMA_BIT_MASK(32) + 1)
> return false;
>
> mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
>
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