Messages in this thread Patch in this message | | | From | YueHaibing <> | Subject | [PATCH v2] ARM: dma-mapping: always clear allocated buffers | Date | Wed, 25 Jul 2018 15:07:06 +0800 |
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Sean Wang reported dma_zalloc_coherent doesn't work as expect on his armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool doesn't honor __GFP_ZERO.
As commit 6829e274a623 ("arm64: dma-mapping: always clear allocated buffers") has pointed out,buffers allocated by dma_alloc_coherent() are always zeroed on most architectures. some drivers rely on this 'feature'. Allocated buffer might be also exposed to userspace with dma_mmap() call,so clearing it is desired from security point of view to avoid exposing random memory to userspace.
This patch unifies dma_alloc_coherent() behavior on ARM architecture with other implementations by unconditionally zeroing allocated buffer.Also to fix dma_zalloc_coherent behavior.
Reported-by: Sean Wang <sean.wang@mediatek.com> Signed-off-by: YueHaibing <yuehaibing@huawei.com> Reviewed-by: zhong jiang <zhongjiang@huawei.com> --- v2: reference more argument from arm64 commit as Christoph suggested --- arch/arm/mm/dma-mapping.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 6656647..cf5882f 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -564,6 +564,7 @@ static void *__alloc_from_pool(size_t size, struct page **ret_page) *ret_page = phys_to_page(phys); ptr = (void *)val; + memset(ptr, 0, size); } return ptr; -- 2.7.0
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