From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 5CB6C6B0271 for ; Tue, 15 Nov 2016 05:57:21 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id x23so98781644pgx.6 for ; Tue, 15 Nov 2016 02:57:21 -0800 (PST) Received: from ozlabs.org (ozlabs.org. [2401:3900:2:1::2]) by mx.google.com with ESMTPS id z2si21818290par.2.2016.11.15.02.57.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Nov 2016 02:57:20 -0800 (PST) From: Michael Ellerman Subject: [PATCH] slab: Add POISON_POINTER_DELTA to ZERO_SIZE_PTR Date: Tue, 15 Nov 2016 21:57:02 +1100 Message-Id: <1479207422-6535-1-git-send-email-mpe@ellerman.id.au> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, keescook@chromium.org 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 --- 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 +#include #include #include @@ -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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org