From patchwork Fri Jun 2 15:20:06 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rik van Riel X-Patchwork-Id: 9762817 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 952B5603F2 for ; Fri, 2 Jun 2017 15:20:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8568E28589 for ; Fri, 2 Jun 2017 15:20:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7A3F928546; Fri, 2 Jun 2017 15:20:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id AF41B285A2 for ; Fri, 2 Jun 2017 15:20:40 +0000 (UTC) Received: (qmail 19616 invoked by uid 550); 2 Jun 2017 15:20:32 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 19588 invoked from network); 2 Jun 2017 15:20:31 -0000 X-Authentication-Warning: annuminas.surriel.com: riel set sender to riel@redhat.com using -f From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: kernel-hardening@lists.openwall.com, akpm@linux-foundation.org, mingo@kernel.org, oleg@redhat.com, lwoodman@redhat.com, mhocko@suse.de, danielmicay@gmail.com, will.deacon@arm.com, benh@kernel.crashing.org Date: Fri, 2 Jun 2017 11:20:06 -0400 Message-Id: <20170602152010.2064-3-riel@redhat.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170602152010.2064-1-riel@redhat.com> References: <20170602152010.2064-1-riel@redhat.com> Subject: [kernel-hardening] [PATCH 2/6] x86/elf: move 32 bit ELF_ET_DYN_BASE to 256MB X-Virus-Scanned: ClamAV using ClamSMTP From: Rik van Riel When setting up mmap_base, we take care to start the mmap base below the maximum extent to which the stack will grow. However, we take no such precautions with PIE binaries, which are placed at 5/6 of TASK_SIZE plus a random offset. As a result, 32 bit PIE binaries can end up smack in the middle of where the stack (which is randomized down) is supposed to go. That problem can be avoided by putting the 32 bit ELF_ET_DYN_BASE at 256MB, which is a value linux-hardened and grsecurity have used for a long time now without any known (to me) bug reports. Signed-off-by: Rik van Riel --- arch/x86/include/asm/elf.h | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index e8ab9a46bc68..dafa098cc05a 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -245,12 +245,23 @@ extern int force_personality32; #define CORE_DUMP_USE_REGSET #define ELF_EXEC_PAGESIZE 4096 +/* + * True on X86_32 or when emulating IA32 on X86_64 + */ +static inline int mmap_is_ia32(void) +{ + return IS_ENABLED(CONFIG_X86_32) || + (IS_ENABLED(CONFIG_COMPAT) && + test_thread_flag(TIF_ADDR32)); +} + /* This is the location that an ET_DYN program is loaded if exec'ed. Typical use of this is to invoke "./ld.so someprog" to test out a new version of the loader. We need to make sure that it is out of the way of the program that it will "exec", and that there is sufficient room for the brk. */ -#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2) +#define ELF_ET_DYN_BASE (mmap_is_ia32() ? 0x10000000UL : \ + (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, @@ -293,16 +304,6 @@ do { \ } \ } while (0) -/* - * True on X86_32 or when emulating IA32 on X86_64 - */ -static inline int mmap_is_ia32(void) -{ - return IS_ENABLED(CONFIG_X86_32) || - (IS_ENABLED(CONFIG_COMPAT) && - test_thread_flag(TIF_ADDR32)); -} - extern unsigned long tasksize_32bit(void); extern unsigned long tasksize_64bit(void); extern unsigned long get_mmap_base(int is_legacy);