POISON_POINTER_DELTA is defined in poison.h, and is intended to be used to shift poison values so that they don't alias userspace. We should add it to ZERO_SIZE_PTR so that attackers can't use ZERO_SIZE_PTR as a way to get a pointer to userspace. Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> --- include/linux/slab.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index 084b12bad198..17ddd7aea2dd 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -12,6 +12,7 @@ #define _LINUX_SLAB_H #include <linux/gfp.h> +#include <linux/poison.h> #include <linux/types.h> #include <linux/workqueue.h> @@ -109,7 +110,7 @@ * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL can. * Both make kfree a no-op. */ -#define ZERO_SIZE_PTR ((void *)16) +#define ZERO_SIZE_PTR ((void *)(16 + POISON_POINTER_DELTA)) #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \ (unsigned long)ZERO_SIZE_PTR) -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>