arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing

We need to invalidate the caches *before* clearing the buffer via the
non-cacheable alias, else in the worst case __dma_flush_area() may
write back dirty lines over the top of our nice new zeros.

Fixes: dd65a941f6ba ("arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag")
Cc: <stable@vger.kernel.org> # 4.18.x-
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.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 a3ac262848451ae49535c37a6997a211b0f5e914..a5370440609917c10fb2f2c4ffbc26f5e1a1ba9f 100644 (file)
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -429,9 +429,9 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
                                                   prot,
                                                   __builtin_return_address(0));
                if (addr) {
-                       memset(addr, 0, size);
                        if (!coherent)
                                __dma_flush_area(page_to_virt(page), iosize);
+                       memset(addr, 0, size);
                } else {
                        iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
                        dma_release_from_contiguous(dev, page,