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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 7BF4AC433DB for ; Tue, 9 Feb 2021 20:18:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B21464E66 for ; Tue, 9 Feb 2021 20:18:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233478AbhBIUSG (ORCPT ); Tue, 9 Feb 2021 15:18:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47643 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233425AbhBIS0Z (ORCPT ); Tue, 9 Feb 2021 13:26:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612895069; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aX0FuUKAs7N1GghNqWcicvh9RDt8EL1arT6ICksgpbE=; b=MFHiblhVP7K1NRUr7pwjzeTzo6ihu9hyzcoqECIibxbAQlDg5NwMqRYkCwW2B2gnjzZqxm tgk96SiEM12EkmCMeEJi2K1YifFO3NLAGnr0dqZ6dj/MYFnwWxY1t8ebussZd2lWN0ge/r FWPlOwe6fBp3yMPT1snRusfFuW3vWAg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-413-3f1BIwV2MqG1abpV4wGKew-1; Tue, 09 Feb 2021 13:24:27 -0500 X-MC-Unique: 3f1BIwV2MqG1abpV4wGKew-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E56F9CC623; Tue, 9 Feb 2021 18:24:25 +0000 (UTC) Received: from treble (ovpn-120-169.rdu2.redhat.com [10.10.120.169]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1C94A19CA8; Tue, 9 Feb 2021 18:24:25 +0000 (UTC) Date: Tue, 9 Feb 2021 12:24:23 -0600 From: Josh Poimboeuf To: Andrey Ryabinin Cc: Peter Zijlstra , Alexander Viro , linux-kernel@vger.kernel.org, Randy Dunlap , dvyukov@google.com, keescook@chromium.org Subject: Re: [PATCH] ubsan: Require GCC-8+ or Clang to use UBSAN Message-ID: <20210209182423.te43h3mmhtvwi2d7@treble> References: <590998aa9cc50f431343f76cae72b2abf8ac1fdd.1608699683.git.jpoimboe@redhat.com> <20210104151317.GR3021@hirez.programming.kicks-ass.net> <20210118175337.rnh2b6vdnqw3ue63@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210118175337.rnh2b6vdnqw3ue63@treble> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 18, 2021 at 11:53:37AM -0600, Josh Poimboeuf wrote: > On Thu, Jan 14, 2021 at 02:09:28PM +0300, Andrey Ryabinin wrote: > > > > > > On 1/14/21 1:59 PM, Peter Zijlstra wrote: > > > On Mon, Jan 04, 2021 at 04:13:17PM +0100, Peter Zijlstra wrote: > > >> On Tue, Dec 22, 2020 at 11:04:54PM -0600, Josh Poimboeuf wrote: > > >>> GCC 7 has a known bug where UBSAN ignores '-fwrapv' and generates false > > >>> signed-overflow-UB warnings. The type mismatch between 'i' and > > >>> 'nr_segs' in copy_compat_iovec_from_user() is causing such a warning, > > >>> which also happens to violate uaccess rules: > > >>> > > >>> lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to __ubsan_handle_add_overflow() with UACCESS enabled > > >>> > > >>> Fix it by making the variable types match. > > >>> > > >>> This is similar to a previous commit: > > >>> > > >>> 29da93fea3ea ("mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions") > > >> > > >> Maybe it's time we make UBSAN builds depend on GCC-8+ ? > > > > > > --- > > > Subject: ubsan: Require GCC-8+ or Clang to use UBSAN > > > > > > Just like how we require GCC-8.2 for KASAN due to compiler bugs, require > > > a sane version of GCC for UBSAN. > > > > > > Specifically, before GCC-8 UBSAN doesn't respect -fwrapv and thinks > > > signed arithmetic is buggered. > > > > > > > Actually removing CONFIG_UBSAN_SIGNED_OVERFLOW would give us the same > > effect without restricting GCC versions. > > Is that preferable? Always happy to remove code, just need some > justification behind it. Andrey, Is Peter's patch acceptable or do you want to do something else? -- Josh