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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: Thomas Tai <thomas.tai@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Thomas Tai 2020-09-17 18:43:03 +02:00 committed by Christoph Hellwig
parent a92df4f62f
commit f959dcd6dd
2 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/dma-direct.h
View File

@ -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;

11
kernel/dma/mapping.c
View File

@ -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;