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=-13.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 6C937C4332B for ; Tue, 24 Mar 2020 08:41:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 41F8C20836 for ; Tue, 24 Mar 2020 08:41:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727148AbgCXIl1 (ORCPT ); Tue, 24 Mar 2020 04:41:27 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:23114 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726129AbgCXIl0 (ORCPT ); Tue, 24 Mar 2020 04:41:26 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02O8XtGS058800 for ; Tue, 24 Mar 2020 04:41:25 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ywbuv4uyg-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 24 Mar 2020 04:41:25 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 24 Mar 2020 08:41:17 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02O8fHBa58327132 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Mar 2020 08:41:17 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 87A22A4051; Tue, 24 Mar 2020 08:41:17 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 62EAAA4069; Tue, 24 Mar 2020 08:41:15 +0000 (GMT) Received: from JAVRIS.in.ibm.com (unknown [9.199.56.74]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 24 Mar 2020 08:41:15 +0000 (GMT) Subject: Re: [PATCH] objtool: Documentation: document UACCESS warnings To: Nick Desaulniers , jpoimboe@redhat.com, peterz@infradead.org Cc: Mauro Carvalho Chehab , Jonathan Corbet , Wolfram Sang , Raphael Gault , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com References: <20200323212538.GN2452@worktop.programming.kicks-ass.net> <20200324001321.39562-1-ndesaulniers@google.com> From: Kamalesh Babulal Date: Tue, 24 Mar 2020 14:11:13 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200324001321.39562-1-ndesaulniers@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20032408-0008-0000-0000-00000362E1E3 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20032408-0009-0000-0000-00004A844D4C Message-Id: <90c16f02-9364-651e-6dea-8758a698d2ce@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-24_02:2020-03-23,2020-03-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 malwarescore=0 bulkscore=0 adultscore=0 mlxscore=0 phishscore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003240042 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/24/20 5:43 AM, Nick Desaulniers wrote: > Compiling with Clang and CONFIG_KASAN=y was exposing a few warnings: > call to memset() with UACCESS enabled > > Document how to fix these for future travelers. > > Link: https://github.com/ClangBuiltLinux/linux/issues/876 > Suggested-by: Peter Zijlstra > Signed-off-by: Nick Desaulniers Looks good, a minor nitpick below. > --- > .../Documentation/stack-validation.txt | 20 +++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/tools/objtool/Documentation/stack-validation.txt b/tools/objtool/Documentation/stack-validation.txt > index de094670050b..156fee13ba02 100644 > --- a/tools/objtool/Documentation/stack-validation.txt > +++ b/tools/objtool/Documentation/stack-validation.txt > @@ -289,6 +289,26 @@ they mean, and suggestions for how to fix them. > might be corrupt due to a gcc bug. For more details, see: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646 > > +9. file.o: warning: objtool: funcA() call to funcB() with UACCESS enabled > + > + This means that an unexpected call to a non-whitelisted function exists > + outside of arch-specific guards. > + X86: SMAP (stac/clac): __uaccess_begin()/__uaccess_end() > + ARM: PAN: uaccess_enable()/uaccess_enable() ^^^^^^ uaccess_disable() > + > + These functions should called to denote a minimal critical section around > + access to __user variables. See also: https://lwn.net/Articles/517475/ -- Kamalesh