From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751923AbcEKKqK (ORCPT ); Wed, 11 May 2016 06:46:10 -0400 Received: from smtpsalv.cc.upv.es ([158.42.249.11]:56131 "EHLO smtpsalv.upv.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751382AbcEKKqJ (ORCPT ); Wed, 11 May 2016 06:46:09 -0400 From: Hector Marco-Gisbert To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Brian Gerst , Andy Lutomirski , Borislav Petkov , Huaitong Han , kees Cook , Ismael Ripoll Ripoll , Hector Marco-Gisbert Subject: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable Date: Wed, 11 May 2016 12:45:02 +0200 Message-Id: <1462963502-11636-1-git-send-email-hecmargi@upv.es> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The READ_IMPLIES_EXEC personality was removed in 2005 for 64-bit processes, (commit a3cc2546a54361b86b73557df5b85c4fc3fc27c3 form history.git). But it's still possible to have all readable areas with EXEC permissions by setting the stack as executable in 64-bit ELF executables (also in 32-bit). This is because the macro elf_read_implies_exec() does not distinguish between 32 and 64-bit executables: when the stack is executable then the read-implies-exec personality is set (enabled) to the process. We think that this is not a desirable behaviour, maybe read-implies-exec could be used via personality but not by setting the stack as executable in the ELF. For x86_64 processes, is there any reason to disable read-implies-exec personality and at the same time enable it when the stack is executable ? With this patch it's no longer possible to enable the read-implies-exec on the process by setting the stack as executable in the PT_GNU_STACK on x86_64 executables. Regarding 32-bits processes, is there any reason to enable read-implies-exec by setting the stack as executable instead of using the personality on X86_32 or when emulating IA32 on X86_64 ? If not, I could re-send the patch which removes this possibility. Signed-off-by: Hector Marco-Gisbert Acked-by: Ismael Ripoll Ripoll --- arch/x86/include/asm/elf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 15340e3..87fd15e 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -271,8 +271,8 @@ extern int force_personality32; * An executable for which elf_read_implies_exec() returns TRUE will * have the READ_IMPLIES_EXEC personality flag set automatically. */ -#define elf_read_implies_exec(ex, executable_stack) \ - (executable_stack != EXSTACK_DISABLE_X) +#define elf_read_implies_exec(ex, executable_stack) \ + (mmap_is_ia32() ? (executable_stack != EXSTACK_DISABLE_X) : 0) struct task_struct; -- 1.9.1