fix LIST_POISON{1,2} offset
PATCH 1/3 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
--- include/linux/poison.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
include/linux/poison.h +2 -2
@@ -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 **********/ /*
Signature · 1 line
2.1.0
PATCH 2/3 use POISON_POINTER_DELTA for poison pointers
TIMER_ENTRY_STATIC and TAIL_MAPPING are defined as poison pointers which should point to nowhere. Redefine them using POISON_POINTER_DELTA arithmetics to make sure they really point to non-mappable area declared by the target architecture.
--- include/linux/poison.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
include/linux/poison.h +2 -2
@@ -27,14 +27,14 @@* Magic number "tsta" to indicate a static timer initializer * for the object debugging code. */ -#define TIMER_ENTRY_STATIC ((void *) 0x74737461) +#define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA)/********** mm/debug-pagealloc.c **********/ #define PAGE_POISON 0xaa/********** mm/page_alloc.c ************/ -#define TAIL_MAPPING ((void *) 0x01014A11 + POISON_POINTER_DELTA) +#define TAIL_MAPPING ((void *) 0x400 + POISON_POINTER_DELTA)/********** mm/slab.c **********/ /*
Signature · 1 line
2.1.0
PATCH 3/3 remove not-used poison pointer macros
--- include/linux/poison.h | 7 ------- 1 file changed, 7 deletions(-)
include/linux/poison.h +0 -7
@@ -73,10 +73,6 @@#define ATM_POISON_FREE 0x12#define ATM_POISON 0xdeadbeef -/********** net/ **********/ -#define NEIGHBOR_DEAD 0xdeadbeef -#define NETFILTER_LINK_POISON 0xdead57ac -/********** kernel/mutexes **********/ #define MUTEX_DEBUG_INIT 0x11#define MUTEX_DEBUG_FREE 0x22
@@ -87,7 +83,4 @@/********** security/ **********/ #define KEY_DESTROY 0xbd -/********** sound/oss/ **********/ -#define OSS_POISON_FREE 0xAB -#endif
Signature · 1 line
2.1.0
Re: [PATCH 2/3] use POISON_POINTER_DELTA for poison pointers
In reply to Vasily KulikovQuoted 15 lines · Vasily Kulikov
TIMER_ENTRY_STATICandTAIL_MAPPINGare defined as poison pointers which should point to nowhere. Redefine them usingPOISON_POINTER_DELTAarithmetics to make sure they really point to non-mappable area declared by the target architecture.Signed-off-by Vasily Kulikov <[email protected]>--- include/linux/poison.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)include/linux/poison.h +0
-0
include/linux/poison.h line 30
Quoted 5 lines
include/linux/poison.h +1
-1@@ -27,14 +27,14 @@* Magic number "tsta" to indicate a static timer initializer * for the object debugging code. */ -#define TIMER_ENTRY_STATIC ((void *) 0x74737461) +#define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA)