From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933162Ab0EJXVJ (ORCPT ); Mon, 10 May 2010 19:21:09 -0400 Received: from kroah.org ([198.145.64.141]:51608 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757428Ab0EJW5c (ORCPT ); Mon, 10 May 2010 18:57:32 -0400 X-Mailbox-Line: From gregkh@kvm.kroah.org Mon May 10 15:35:35 2010 Message-Id: <20100510223535.427211037@kvm.kroah.org> User-Agent: quilt/0.48-4.4 Date: Mon, 10 May 2010 15:34:23 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jaswinder Singh Rajput , Ingo Molnar , Avi Kivity Subject: [11/98] core, x86: make LIST_POISON less deadly In-Reply-To: <20100510223714.GA18416@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Avi Kivity commit a29815a333c6c6e677294bbe5958e771d0aad3fd upstream. The list macros use LIST_POISON1 and LIST_POISON2 as undereferencable pointers in order to trap erronous use of freed list_heads. Unfortunately userspace can arrange for those pointers to actually be dereferencable, potentially turning an oops to an expolit. To avoid this allow architectures (currently x86_64 only) to override the default values for these pointers with truly-undereferencable values. This is easy on x86_64 as the virtual address space is large and contains areas that cannot be mapped. Other 64-bit architectures will likely find similar unmapped ranges. [ingo: switch to 0xdead000000000000 as the unmapped area] [ingo: add comments, cleanup] [jaswinder: eliminate sparse warnings] Acked-by: Linus Torvalds Signed-off-by: Jaswinder Singh Rajput Signed-off-by: Ingo Molnar Signed-off-by: Avi Kivity Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/x86/Kconfig | 5 +++++ include/linux/poison.h | 16 ++++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1236,6 +1236,11 @@ config ARCH_MEMORY_PROBE def_bool X86_64 depends on MEMORY_HOTPLUG +config ILLEGAL_POINTER_VALUE + hex + default 0 if X86_32 + default 0xdead000000000000 if X86_64 + source "mm/Kconfig" config HIGHPTE --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -2,13 +2,25 @@ #define _LINUX_POISON_H /********** include/linux/list.h **********/ + +/* + * Architectures might want to move the poison pointer offset + * into some well-recognized area such as 0xdead000000000000, + * that is also not mappable by user-space exploits: + */ +#ifdef CONFIG_ILLEGAL_POINTER_VALUE +# define POISON_POINTER_DELTA _AC(CONFIG_ILLEGAL_POINTER_VALUE, UL) +#else +# define POISON_POINTER_DELTA 0 +#endif + /* * These are non-NULL pointers that will result in page faults * under normal circumstances, used to verify that nobody uses * non-initialized list entries. */ -#define LIST_POISON1 ((void *) 0x00100100) -#define LIST_POISON2 ((void *) 0x00200200) +#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA) +#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA) /********** include/linux/timer.h **********/ /*