Reply-To: kernel-hardening@lists.openwall.com Sender: Vasiliy Kulikov Date: Sun, 26 Jul 2015 16:43:24 +0300 From: Vasily Kulikov Message-ID: <20150726134324.GA1068@cachalot> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [kernel-hardening] [PATCH 1/3] fix LIST_POISON{1,2} offset To: linux-kernel@vger.kernel.org Cc: Randy Dunlap , Andrew Morton , kernel-hardening@lists.openwall.com, Ingo Molnar List-ID: 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 Signed-off-by: Vasily Kulikov --- 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 7b2a7fc..ee697b9 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 **********/ /* -- 2.1.0