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

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 6829e274a623 ("arm64: dma-mapping: always clear allocated
buffers").

Fixes: 44176bb38fa4 ("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
index 49e217ac7e1ec2087c440c60ec71126f0e48ec32..61e93f0b548228f57a08f25a14291a1e46437115 100644 (file)
--- 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);