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 <[email protected]>
Signed-off-by: YueHaibing <[email protected]>
Reviewed-by: zhong jiang <[email protected]>
---
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
