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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Subject: [PATCH 4.19 13/44] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
Date:   Tue, 18 Dec 2018 17:39:25 +0100
Message-Id: <20181218163929.091027618@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Robin Murphy <robin.murphy@arm.com>

commit 3238c359acee4ab57f15abb5a82b8ab38a661ee7 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/mm/dma-mapping.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -587,9 +587,9 @@ static void *__iommu_alloc_attrs(struct
 						   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,