Russell, will you pick this patch?
On 2018/7/25 15:13, YueHaibing wrote: > +CC Christoph Hellwig <h...@infradead.org> > > On 2018/7/25 15:07, YueHaibing wrote: >> 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.w...@mediatek.com> >> Signed-off-by: YueHaibing <yuehaib...@huawei.com> >> Reviewed-by: zhong jiang <zhongji...@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; >>