4.6-stable review patch. If anyone has any objections, please let me know.
------------------ From: Shaokun Zhang <[email protected]> commit 20c27a4270c775d7ed661491af8ac03264d60fc6 upstream. __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 7249b79f6b4cc ("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 <[email protected]> Cc: Will Deacon <[email protected]> Cc: Mark Rutland <[email protected]> Reviewed-by: Catalin Marinas <[email protected]> Signed-off-by: Shaokun Zhang <[email protected]> Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm64/mm/flush.c | 4 ---- 1 file changed, 4 deletions(-) --- a/arch/arm64/mm/flush.c +++ b/arch/arm64/mm/flush.c @@ -71,10 +71,6 @@ void __sync_icache_dcache(pte_t pte, uns { 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)) sync_icache_aliases(page_address(page), PAGE_SIZE << compound_order(page));
