From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934589AbZJIX0v (ORCPT ); Fri, 9 Oct 2009 19:26:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934521AbZJIX0t (ORCPT ); Fri, 9 Oct 2009 19:26:49 -0400 Received: from kroah.org ([198.145.64.141]:56321 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934517AbZJIX0s (ORCPT ); Fri, 9 Oct 2009 19:26:48 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Fri Oct 9 16:22:34 2009 Message-Id: <20091009232234.069019937@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Fri, 09 Oct 2009 16:21:28 -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, Michal Hocko , Jiri Kosina , "H. Peter Anvin" , Chuck Ebbert Subject: [5/8] x86: Increase MIN_GAP to include randomized stack From: gregkh@mini.kroah.org References: <20091009232123.464253035@mini.kroah.org> Content-Disposition: inline; filename=x86-increase-min_gap-to-include-randomized-stack.patch In-Reply-To: <20091009232300.GA403@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko [ trivial backport to 2.6.27: Chuck Ebbert ] commit 80938332d8cf652f6b16e0788cf0ca136befe0b5 upstream. Currently we are not including randomized stack size when calculating mmap_base address in arch_pick_mmap_layout for topdown case. This might cause that mmap_base starts in the stack reserved area because stack is randomized by 1GB for 64b (8MB for 32b) and the minimum gap is 128MB. If the stack really grows down to mmap_base then we can get silent mmap region overwrite by the stack values. Let's include maximum stack randomization size into MIN_GAP which is used as the low bound for the gap in mmap. Signed-off-by: Michal Hocko LKML-Reference: <1252400515-6866-1-git-send-email-mhocko@suse.cz> Acked-by: Jiri Kosina Signed-off-by: H. Peter Anvin Cc: Chuck Ebbert Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/mmap.c | 17 +++++++++++++++-- include/asm-x86/elf.h | 2 ++ 2 files changed, 17 insertions(+), 2 deletions(-) --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -29,13 +29,26 @@ #include #include #include +#include + +static unsigned int stack_maxrandom_size(void) +{ + unsigned int max = 0; + if ((current->flags & PF_RANDOMIZE) && + !(current->personality & ADDR_NO_RANDOMIZE)) { + max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT; + } + + return max; +} + /* * Top of mmap area (just below the process stack). * - * Leave an at least ~128 MB hole. + * Leave an at least ~128 MB hole with possible stack randomization. */ -#define MIN_GAP (128*1024*1024) +#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size()) #define MAX_GAP (TASK_SIZE/6*5) /* --- a/include/asm-x86/elf.h +++ b/include/asm-x86/elf.h @@ -287,6 +287,8 @@ do { \ #ifdef CONFIG_X86_32 +#define STACK_RND_MASK (0x7ff) + #define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO)) #define ARCH_DLINFO ARCH_DLINFO_IA32(vdso_enabled)