From 1414c7f4f7d72d138fff35f00151d15749b5beda Mon Sep 17 00:00:00 2001
From: Laura Abbott <labbott@fedoraproject.org>
Date: Tue, 15 Mar 2016 14:56:30 -0700
Subject: mm/page_poisoning.c: allow for zero poisoning

By default, page poisoning uses a poison value (0xaa) on free.  If this
is changed to 0, the page is not only sanitized but zeroing on alloc
with __GFP_ZERO can be skipped as well.  The tradeoff is that detecting
corruption from the poisoning is harder to detect.  This feature also
cannot be used with hibernation since pages are not guaranteed to be
zeroed after hibernation.

Credit to Grsecurity/PaX team for inspiring this work

Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/poison.h | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'include/linux/poison.h')

diff --git a/include/linux/poison.h b/include/linux/poison.h
index 4a27153574e2..51334edec506 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -30,7 +30,11 @@
 #define TIMER_ENTRY_STATIC	((void *) 0x300 + POISON_POINTER_DELTA)
 
 /********** mm/debug-pagealloc.c **********/
+#ifdef CONFIG_PAGE_POISONING_ZERO
+#define PAGE_POISON 0x00
+#else
 #define PAGE_POISON 0xaa
+#endif
 
 /********** mm/page_alloc.c ************/
 
-- 
cgit v1.2.3