Commit b12d6627 authored Nov 07, 2019 by Nicolas Saenz Julienne Committed by Christoph Hellwig Nov 11, 2019

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 0xc0000000. 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 <nsaenzjulienne@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent 5e76f564

include/linux/dma-direct.h

+10 −2

Original line number	Diff line number	Diff line
		@@ -3,8 +3,11 @@
		#define _LINUX_DMA_DIRECT_H 1

		#include <linux/dma-mapping.h>
		#include <linux/memblock.h> /* for min_low_pfn */
		#include <linux/mem_encrypt.h>

		static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr);

		#ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
		#include <asm/dma-direct.h>
		#else
		@@ -24,11 +27,16 @@ static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)

		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;

		return addr + size - 1 <=
		min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
		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);
		}
		#endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */

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