Patch "arm64: dma-mapping: always clear allocated buffers" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

arm64: dma-mapping: always clear allocated buffers

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm64-dma-mapping-always-clear-allocated-buffers.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marek Szyprowski <[email protected]>
Date: Thu, 23 Apr 2015 12:46:16 +0100
Subject: arm64: dma-mapping: always clear allocated buffers

From: Marek Szyprowski <[email protected]>

commit 6829e274a623187c24f7cfc0e3d35f25d087fcc5 upstream.

Buffers allocated by dma_alloc_coherent() are always zeroed on Alpha, ARM (32bit), MIPS, PowerPC, x86/x86_64 and probably other architectures. It turned out that 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 ARM64 architecture with other implementations by unconditionally zeroing allocated buffer.

---
 arch/arm64/mm/dma-mapping.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

@@ -67,8 +67,7 @@ static void *__alloc_from_pool(size_t si
 
 		*ret_page = phys_to_page(phys);
 		ptr = (void *)val;
-		if (flags & __GFP_ZERO)
-			memset(ptr, 0, size);
+		memset(ptr, 0, size);
 	}
 
 	return ptr;

@@ -113,8 +112,7 @@ static void *__dma_alloc_coherent(struct
 
 		*dma_handle = phys_to_dma(dev, page_to_phys(page));
 		addr = page_address(page);
-		if (flags & __GFP_ZERO)
-			memset(addr, 0, size);
+		memset(addr, 0, size);
 		return addr;
 	} else {
 		return swiotlb_alloc_coherent(dev, size, dma_handle, flags);

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/arm64-dma-mapping-always-clear-allocated-buffers.patch