arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag

mszyprow · ctmarinas · commit dd65a941f6ba · 2018-06-19T14:19:21.000+01:00
dma_alloc_*() buffers might be exposed to userspace via mmap() call, so they should be cleared on allocation. In case of IOMMU-based dma-mapping implementation such buffer clearing was missing in the code path for DMA_ATTR_FORCE_CONTIGUOUS flag handling, because dma_alloc_from_contiguous() doesn't honor __GFP_ZERO flag. This patch fixes this issue. For more information on clearing buffers allocated by dma_alloc_* functions, see commit 6829e27 ("arm64: dma-mapping: always clear allocated buffers"). Fixes: 44176bb ("arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to IOMMU") Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
@@ -583,13 +583,14 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
 						    size >> PAGE_SHIFT);
 			return NULL;
 		}
-		if (!coherent)
-			__dma_flush_area(page_to_virt(page), iosize);
-
 		addr = dma_common_contiguous_remap(page, size, VM_USERMAP,
 						   prot,
 						   __builtin_return_address(0));
-		if (!addr) {
+		if (addr) {
+			memset(addr, 0, size);
+			if (!coherent)
+				__dma_flush_area(page_to_virt(page), iosize);
+		} else {
 			iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
 			dma_release_from_contiguous(dev, page,
 						    size >> PAGE_SHIFT);
