From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61627C43219 for ; Sat, 27 Apr 2019 15:29:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36747208C2 for ; Sat, 27 Apr 2019 15:29:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728589AbfD0P3J (ORCPT ); Sat, 27 Apr 2019 11:29:09 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:32910 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727281AbfD0PPT (ORCPT ); Sat, 27 Apr 2019 11:15:19 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP2q-0000zM-4m; Sat, 27 Apr 2019 16:15:16 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2n-0004dM-Ei; Sat, 27 Apr 2019 16:15:13 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Peter Zijlstra" , "Denys Vlasenko" , "Josh Poimboeuf" , "Brian Gerst" , "Andy Lutomirski" , "Borislav Petkov" , "Linus Torvalds" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 176/202] x86/uaccess: Don't leak the AC flag into __put_user() value evaluation In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 2a418cf3f5f1caf911af288e978d61c9844b0695 upstream. When calling __put_user(foo(), ptr), the __put_user() macro would call foo() in between __uaccess_begin() and __uaccess_end(). If that code were buggy, then those bugs would be run without SMAP protection. Fortunately, there seem to be few instances of the problem in the kernel. Nevertheless, __put_user() should be fixed to avoid doing this. Therefore, evaluate __put_user()'s argument before setting AC. This issue was noticed when an objtool hack by Peter Zijlstra complained about genregs_get() and I compared the assembly output to the C source. [ bp: Massage commit message and fixed up whitespace. ] Fixes: 11f1a4b9755f ("x86: reorganize SMAP handling in user space accesses") Signed-off-by: Andy Lutomirski Signed-off-by: Borislav Petkov Acked-by: Linus Torvalds Cc: Peter Zijlstra Cc: Brian Gerst Cc: Josh Poimboeuf Cc: Denys Vlasenko Link: http://lkml.kernel.org/r/20190225125231.845656645@infradead.org [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -311,8 +311,7 @@ do { \ __put_user_asm(x, ptr, retval, "l", "k", "ir", errret); \ break; \ case 8: \ - __put_user_asm_u64((__typeof__(*ptr))(x), ptr, retval, \ - errret); \ + __put_user_asm_u64(x, ptr, retval, errret); \ break; \ default: \ __put_user_bad(); \ @@ -423,8 +422,10 @@ do { \ #define __put_user_nocheck(x, ptr, size) \ ({ \ int __pu_err; \ + __typeof__(*(ptr)) __pu_val; \ + __pu_val = x; \ __uaccess_begin(); \ - __put_user_size((x), (ptr), (size), __pu_err, -EFAULT); \ + __put_user_size(__pu_val, (ptr), (size), __pu_err, -EFAULT); \ __uaccess_end(); \ __pu_err; \ })