Patch "arm64: mm: Fix freeing of the wrong memmap entries with !SPARSEMEM_VMEMMAP" has been added to the 4.1-stable tree

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

arm64: mm: Fix freeing of the wrong memmap entries with !SPARSEMEM_VMEMMAP

to the 4.1-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-mm-fix-freeing-of-the-wrong-memmap-entries-with-sparsemem_vmemmap.patch
and it can be found in the queue-4.1 subdirectory.

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

From: Dave P Martin <[email protected]>
Date: Tue, 16 Jun 2015 17:38:47 +0100
Subject: arm64: mm: Fix freeing of the wrong memmap entries with !SPARSEMEM_VMEMMAP

From: Dave P Martin <[email protected]>

commit b9bcc919931611498e856eae9bf66337330d04cc upstream.

The memmap freeing code in free_unused_memmap() computes the end of each memblock by adding the memblock size onto the base. However, if SPARSEMEM is enabled then the value (start) used for the base may already have been rounded downwards to work out which memmap entries to free after the previous memblock.

This may cause memmap entries that are in use to get freed.

In general, you're not likely to hit this problem unless there are at least 2 memblocks and one of them is not aligned to a sparsemem section boundary. Note that carve-outs can increase the number of memblocks by splitting the regions listed in the device tree.

This problem doesn't occur with SPARSEMEM_VMEMMAP, because the vmemmap code deals with freeing the unused regions of the memmap instead of requiring the arch code to do it.

This patch gets the memblock base out of the memblock directly when computing the block end address to ensure the correct value is used.

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

@@ -262,7 +262,7 @@ static void __init free_unused_memmap(vo
 		 * memmap entries are valid from the bank end aligned to
 		 * MAX_ORDER_NR_PAGES.
 		 */
-		prev_end = ALIGN(start + __phys_to_pfn(reg->size),
+		prev_end = ALIGN(__phys_to_pfn(reg->base + reg->size),
 				 MAX_ORDER_NR_PAGES);
 	}
 

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

queue-4.1/arm64-mm-fix-freeing-of-the-wrong-memmap-entries-with-sparsemem_vmemmap.patch