Commit 0868e8dd authored Jun 21, 2016 by Shaokun Zhang Committed by Sasha Levin Jul 12, 2016

arm64: mm: remove page_mapping check in __sync_icache_dcache



[ Upstream commit 20c27a4270c775d7ed661491af8ac03264d60fc6 ]

__sync_icache_dcache unconditionally skips the cache maintenance for
anonymous pages, under the assumption that flushing is only required in
the presence of D-side aliases [see 7249b79f ("arm64: Do not flush
the D-cache for anonymous pages")].

Unfortunately, this breaks migration of anonymous pages holding
self-modifying code, where userspace cannot be reasonably expected to
reissue maintenance instructions in response to a migration.

This patch fixes the problem by removing the broken page_mapping(page)
check from the cache syncing code, otherwise we may end up fetching and
executing stale instructions from the PoU.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

parent 673a67b9

arch/arm64/mm/flush.c

+0 −4

Original line number	Diff line number	Diff line
		@@ -74,10 +74,6 @@ void __sync_icache_dcache(pte_t pte, unsigned long addr)
		{
		struct page *page = pte_page(pte);

		/* no flushing needed for anonymous pages */
		if (!page_mapping(page))
		return;

		if (!test_and_set_bit(PG_dcache_clean, &page->flags)) {
		__flush_dcache_area(page_address(page),
		PAGE_SIZE << compound_order(page));