[87/99] vmscan: limit VM_EXEC protection to file pages

[Greg KH]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>

commit 41e20983fe553b39bc2b00e07c7a379f0c86a4bc upstream.

It is possible to have !Anon but SwapBacked pages, and some apps could
create huge number of such pages with MAP_SHARED|MAP_ANONYMOUS.  These
pages go into the ANON lru list, and hence shall not be protected: we only
care mapped executable files.  Failing to do so may trigger OOM.

Tested-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1298,7 +1298,7 @@ static void shrink_active_list(unsigned 
 			 * IO, plus JVM can create lots of anon VM_EXEC pages,
 			 * so we ignore them here.
 			 */
-			if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
+			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
 				list_add(&page->lru, &l_active);
 				continue;
 			}


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