Re: [PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses
On Wed, 2019-10-30 at 14:41 -0700, Christoph Hellwig wrote:
> On Fri, Oct 18, 2019 at 01:00:43PM +0200, Nicolas Saenz Julienne wrote:
> > +#ifndef CONFIG_ARCH_DMA_ADDR_T_64BIT
> > + /* Check if DMA address overflowed */
> > + if (min(addr, addr + size - 1) <
> > + __phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT)))
> > + return false;
> > +#endif
>
> Would be nice to use IS_ENABLED and PFN_PHYS here, and I also think we
> need to use phys_to_dma to take care of the encryption bit. If you then
> also introduce an end variable we can make the whole thing actually look
> nice:
>
> static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t
> size)
> {
> dma_addr_t end = addr + size - 1;
>
> if (!dev->dma_mask)
> return false;
>
> if (!IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
> min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
> return false;
>
> return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
> }
>
> Otherwise this looks sensible to me.
Thanks, noted.
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Re: [PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses
On Fri, Oct 18, 2019 at 01:00:43PM +0200, Nicolas Saenz Julienne wrote:
> +#ifndef CONFIG_ARCH_DMA_ADDR_T_64BIT
> + /* Check if DMA address overflowed */
> + if (min(addr, addr + size - 1) <
> + __phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT)))
> + return false;
> +#endif
Would be nice to use IS_ENABLED and PFN_PHYS here, and I also think we
need to use phys_to_dma to take care of the encryption bit. If you then
also introduce an end variable we can make the whole thing actually look
nice:
static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
{
dma_addr_t end = addr + size - 1;
if (!dev->dma_mask)
return false;
if (!IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
return false;
return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
}
Otherwise this looks sensible to me.
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[PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses
As seen on the new Raspberry Pi 4 and sta2x11's DMA implementation it is possible for a device configured with 32 bit DMA addresses and a partial DMA mapping located at the end of the address space to overflow. It happens when a higher physical address, not DMAable, is translated to it's DMA counterpart. For example the Raspberry Pi 4, configurable up to 4 GB of memory, has an interconnect capable of addressing the lower 1 GB of physical memory with a DMA offset of 0xc000. It transpires that, any attempt to translate physical addresses higher than the first GB will result in an overflow which dma_capable() can't detect as it only checks for addresses bigger then the maximum allowed DMA address. Fix this by verifying in dma_capable() if the DMA address range provided is at any point lower than the minimum possible DMA address on the bus. Signed-off-by: Nicolas Saenz Julienne --- include/linux/dma-direct.h | 8 1 file changed, 8 insertions(+) diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index adf993a3bd58..af4bb9c81ccc 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h @@ -3,6 +3,7 @@ #define _LINUX_DMA_DIRECT_H 1 #include +#include /* for min_low_pfn */ #include #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA @@ -27,6 +28,13 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size) if (!dev->dma_mask) return false; +#ifndef CONFIG_ARCH_DMA_ADDR_T_64BIT + /* Check if DMA address overflowed */ + if (min(addr, addr + size - 1) < + __phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT))) + return false; +#endif + return addr + size - 1 <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask); } -- 2.23.0 ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
