From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755973AbdKCXEd (ORCPT ); Fri, 3 Nov 2017 19:04:33 -0400 Received: from mail-oi0-f66.google.com ([209.85.218.66]:49113 "EHLO mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752446AbdKCXEb (ORCPT ); Fri, 3 Nov 2017 19:04:31 -0400 X-Google-Smtp-Source: ABhQp+S/cqiiCJ7dsPqbMp3UQTzLkWIaXTBLbNlt77FK8OR3sPGI5DMq6uLCS+99qkYzxmt/vX58XQ== From: Laura Abbott To: kernel-hardening@lists.openwall.com Cc: Laura Abbott , linux-kernel@vger.kernel.org, Mark Rutland , Kees Cook , x86@kernel.org Subject: [RFC PATCH 1/2] x86: Avoid multiple evaluations in __{get,put}_user_size Date: Fri, 3 Nov 2017 16:04:25 -0700 Message-Id: <20171103230426.19114-1-labbott@redhat.com> X-Mailer: git-send-email 2.13.5 In-reply-to: <20171026090942.7041-1-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently __{get,put}_user_size() expand their ptr argument in several places, and some callers pass in expressions with side effects. For example, fs/binfmt_elf.c, passes sp++ as the ptr argument to a chain of __put_user() calls. So far this isn't a problem, as each of these uses is mutually exclusive. However, in subsequent patches we will need to make use of the ptr argument several times, and ensure that we evaluate the ptr expression exactly once to avoid corrupting the pointer. In preparation for such uses, this patch reorganises __{get,put}_user_size to evaluate the ptr argument into a temporary __{gu,pu}_ptr variable, ensuring that side-effects occur exaclty once. There should be no functional change as a result of this patch. Based on work done for arm64 by Mark Rutland. Signed-off-by: Laura Abbott --- This is setup patch for checking __{get,put}_user on x86 based on Mark Rutland's work for arm64 lkml.kernel.org/r/<20171026090942.7041-1-mark.rutland@arm.com> --- arch/x86/include/asm/uaccess.h | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 574dff4d2913..d23fb5844404 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -275,21 +275,25 @@ extern void __put_user_8(void); #define __put_user_size(x, ptr, size, retval, errret) \ do { \ + typeof(ptr) __pu_ptr = (ptr); \ retval = 0; \ - __chk_user_ptr(ptr); \ + __chk_user_ptr(__pu_ptr); \ switch (size) { \ case 1: \ - __put_user_asm(x, ptr, retval, "b", "b", "iq", errret); \ + __put_user_asm(x, __pu_ptr, retval, "b", "b", "iq", \ + errret); \ break; \ case 2: \ - __put_user_asm(x, ptr, retval, "w", "w", "ir", errret); \ + __put_user_asm(x, __pu_ptr, retval, "w", "w", "ir", \ + errret); \ break; \ case 4: \ - __put_user_asm(x, ptr, retval, "l", "k", "ir", errret); \ + __put_user_asm(x, __pu_ptr, retval, "l", "k", "ir", \ + errret); \ break; \ case 8: \ - __put_user_asm_u64((__typeof__(*ptr))(x), ptr, retval, \ - errret); \ + __put_user_asm_u64((__typeof__(*ptr))(x), __pu_ptr, \ + retval, \ errret); \ break; \ default: \ __put_user_bad(); \ @@ -352,20 +356,24 @@ do { \ #define __get_user_size(x, ptr, size, retval, errret) \ do { \ + typeof(ptr) __gu_ptr = (ptr); \ retval = 0; \ - __chk_user_ptr(ptr); \ + __chk_user_ptr(__gu_ptr); \ switch (size) { \ case 1: \ - __get_user_asm(x, ptr, retval, "b", "b", "=q", errret); \ + __get_user_asm(x, __gu_ptr, retval, "b", "b", "=q", \ + errret); \ break; \ case 2: \ - __get_user_asm(x, ptr, retval, "w", "w", "=r", errret); \ + __get_user_asm(x, __gu_ptr, retval, "w", "w", "=r", \ + errret); \ break; \ case 4: \ - __get_user_asm(x, ptr, retval, "l", "k", "=r", errret); \ + __get_user_asm(x, __gu_ptr, retval, "l", "k", "=r", \ + errret); \ break; \ case 8: \ - __get_user_asm_u64(x, ptr, retval, errret); \ + __get_user_asm_u64(x, __gu_ptr, retval, errret); \ break; \ default: \ (x) = __get_user_bad(); \ -- 2.13.5