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include/linux/poison.h: fix LIST_POISON{1,2} offset

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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: Ie2121a417b6a43ee6d119c996b5ec2ad6d01a0a7
Signed-off-by: Yuan Lin <yualin@google.com>
This commit is contained in:
Vasily Kulikov 2016-01-08 14:33:04 -05:00 committed by Yuan Lin
parent 8ba26315f9
commit d965aca981
1 changed files with 2 additions and 2 deletions
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4
include/linux/poison.h
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@ -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 **********/
/*