From ceb75e5cd9b88c1f7872d713728830cf40725d2a Mon Sep 17 00:00:00 2001
From: Vasily Kulikov <segoon@openwall.com>
Date: Fri, 8 Jan 2016 11:19:14 -0500
Subject: [PATCH] include/linux/poison.h: fix LIST_POISON{1,2} offset
Poison pointer values should be small enough to find a room in
non-mmap'able/hardly-mmap'able space. E.g. on x86 "poison pointer space"
is located starting from 0x0. Given unprivileged users cannot mmap
anything below mmap_min_addr, it should be safe to use poison pointers
lower than mmap_min_addr.
The current poison pointer values of LIST_POISON{1,2} might be too big for
mmap_min_addr values equal or less than 1 MB (common case, e.g. Ubuntu
uses only 0x10000). There is little point to use such a big value given
the "poison pointer space" below 1 MB is not yet exhausted. Changing it
to a smaller value solves the problem for small mmap_min_addr setups.
The values are suggested by Solar Designer:
http://www.openwall.com/lists/oss-security/2015/05/02/6
Bug: 26186802
Change-Id: I2663f4e4d8725547c90ea14e082f10ae0cf80679
Signed-off-by: Yuan Lin <yualin@google.com>
---
include/linux/poison.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 2110a81c5e2a..253c9b4198ef 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -19,8 +19,8 @@
* under normal circumstances, used to verify that nobody uses
* non-initialized list entries.
*/
-#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
-#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)
+#define LIST_POISON1 ((void *) 0x100 + POISON_POINTER_DELTA)
+#define LIST_POISON2 ((void *) 0x200 + POISON_POINTER_DELTA)
/********** include/linux/timer.h **********/
/*
--
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