Commit f959dcd6 authored by Thomas Tai's avatar Thomas Tai Committed by Christoph Hellwig
Browse files

dma-direct: Fix potential NULL pointer dereference 



When booting the kernel v5.9-rc4 on a VM, the kernel would panic when
printing a warning message in swiotlb_map(). The dev->dma_mask must not
be a NULL pointer when calling the dma mapping layer. A NULL pointer
check can potentially avoid the panic.

Signed-off-by: default avatarThomas Tai <thomas.tai@oracle.com>
Reviewed-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent a92df4f6

include/linux/dma-direct.h

+0 −3
Original line number Diff line number Diff line
@@ -62,9 +62,6 @@ 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_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&

	    min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))

		return false;

kernel/dma/mapping.c

+11 −0
Original line number Diff line number Diff line
@@ -144,6 +144,10 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page, 
	dma_addr_t addr;



	BUG_ON(!valid_dma_direction(dir));



	if (WARN_ON_ONCE(!dev->dma_mask))

		return DMA_MAPPING_ERROR;



	if (dma_map_direct(dev, ops))

		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);

	else
@@ -179,6 +183,10 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, 
	int ents;



	BUG_ON(!valid_dma_direction(dir));



	if (WARN_ON_ONCE(!dev->dma_mask))

		return 0;



	if (dma_map_direct(dev, ops))

		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);

	else
@@ -213,6 +221,9 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr, 


	BUG_ON(!valid_dma_direction(dir));



	if (WARN_ON_ONCE(!dev->dma_mask))

		return DMA_MAPPING_ERROR;



	/* Don't allow RAM to be mapped */

	if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))

		return DMA_MAPPING_ERROR;

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