Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751921AbdHGUPr (ORCPT ); Mon, 7 Aug 2017 16:15:47 -0400 Received: from mail-pg0-f42.google.com ([74.125.83.42]:36882 "EHLO mail-pg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751505AbdHGUPp (ORCPT ); Mon, 7 Aug 2017 16:15:45 -0400 Date: Mon, 7 Aug 2017 13:15:42 -0700 From: Kees Cook To: Andrew Morton Cc: Kostya Serebryany , Evgeniy Stepanov , Daniel Micay , Dmitry Vyukov , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Pratyush Anand , Dong Bo , Dmitry Safonov , Rik van Riel , Andy Lutomirski , Grzegorz Andrejczuk , linux-arm-kernel@lists.infradead.org, Reid Kleckner , Peter Collingbourne , linux-kernel@vger.kernel.org Subject: [PATCH] mm: Revert x86_64 and arm64 ELF_ET_DYN_BASE base Message-ID: <20170807201542.GA21271@beast> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2887 Lines: 72 Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000 broke AddressSanitizer. This is a partial revert of: commit eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE") commit 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB") The AddressSanitizer tool has hard-coded expectations about where executable mappings are loaded. The motivation for changing the PIE base in the above commits was to avoid the Stack-Clash CVEs that allowed executable mappings to get too close to heap and stack. This was mainly a problem on 32-bit, but the 64-bit bases were moved too, in an effort to proactively protect those systems (proofs of concept do exist that show 64-bit collisions, but other recent changes to fix stack accounting and setuid behaviors will minimize the impact). The new 32-bit PIE base is fine for ASan (since it matches the ET_EXEC base), so only the 64-bit PIE base needs to be reverted to let x86 and arm64 ASan binaries run again. Future changes to the 64-bit PIE base on these architectures can be made optional once a more dynamic method for dealing with AddressSanitizer is found. (e.g. always loading PIE into the mmap region for marked binaries.) Reported-by: Kostya Serebryany Cc: stable@vger.kernel.org Signed-off-by: Kees Cook --- arch/arm64/include/asm/elf.h | 4 ++-- arch/x86/include/asm/elf.h | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index acae781f7359..3288c2b36731 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -114,10 +114,10 @@ /* * This is the base location for PIE (ET_DYN with INTERP) loads. On - * 64-bit, this is raised to 4GB to leave the entire 32-bit address + * 64-bit, this is above 4GB to leave the entire 32-bit address * space open for things that want to use the area for 32-bit pointers. */ -#define ELF_ET_DYN_BASE 0x100000000UL +#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) #ifndef __ASSEMBLY__ diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 1c18d83d3f09..9aeb91935ce0 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -247,11 +247,11 @@ extern int force_personality32; /* * This is the base location for PIE (ET_DYN with INTERP) loads. On - * 64-bit, this is raised to 4GB to leave the entire 32-bit address + * 64-bit, this is above 4GB to leave the entire 32-bit address * space open for things that want to use the area for 32-bit pointers. */ #define ELF_ET_DYN_BASE (mmap_is_ia32() ? 0x000400000UL : \ - 0x100000000UL) + (TASK_SIZE / 3 * 2)) /* This yields a mask that user programs can use to figure out what instruction set this CPU supports. This could be done in user space, -- 2.7.4 -- Kees Cook Pixel Security