mm: Mark free pages as read only

Drivers have a tendency to scribble on everything, including free
pages. Make life easier by marking free pages as read only when
on the buddy list and re-marking as read/write when allocating.

Change-Id: I978ed2921394919917307b9c99217fdc22f82c59
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
(cherry picked from commit 752f5aecb0511c4d661dce2538c723675c1e6449)

1 files changed, 10 insertions, 0 deletions

diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index 5bf5906ce13b..feae18981174 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -6,6 +6,14 @@
 #include <linux/poison.h>
 #include <linux/ratelimit.h>
 
+#ifndef mark_addr_rdonly
+#define mark_addr_rdonly(a)
+#endif
+
+#ifndef mark_addr_rdwrite
+#define mark_addr_rdwrite(a)
+#endif
+
 static bool page_poisoning_enabled __read_mostly;
 
 static bool need_page_poisoning(void)
@@ -59,6 +67,7 @@ static void poison_page(struct page *page)
 
 	set_page_poison(page);
 	memset(addr, PAGE_POISON, PAGE_SIZE);
+	mark_addr_rdonly(addr);
 	kunmap_atomic(addr);
 }
 
@@ -113,6 +122,7 @@ static void unpoison_page(struct page *page)
 
 	addr = kmap_atomic(page);
 	check_poison_mem(addr, PAGE_SIZE);
+	mark_addr_rdwrite(addr);
 	clear_page_poison(page);
 	kunmap_atomic(addr);
 }