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=-5.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 0E461C3F2D2 for ; Thu, 5 Mar 2020 17:04:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D57EF20870 for ; Thu, 5 Mar 2020 17:04:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FiF59DD7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726184AbgCEREN (ORCPT ); Thu, 5 Mar 2020 12:04:13 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:35008 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725944AbgCEREN (ORCPT ); Thu, 5 Mar 2020 12:04:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description; bh=vF3Qg1jYVPL0fMpAIJJ4hQLf8PLL9mugK11wImvRR4I=; b=FiF59DD7vx7aBlltd/4aw7x57/ GaZd9usctGv0IU3Gl089qW9i9VcxMvq97k5+zt7P+tTeB0UTg3pyvjtMTKVaa6HVDvI8GwzqU2S13 F1zzzkUHDo3n7j9zwXeZiJuSLU8RpMJCgIqqxUq3S5XUTuMz1SiMXsf6DAop0haWe7IgS42lp0V4D 1ZyjHXa2tZWiSiN2mTNPkmPsmRPBqyj7mPDQR0wUJpoKsUdozDTNoTGxj09l/y5T9j+Xy6TlsjhMQ 6NYn2Xy/k+vUzXzlyvbY7B46PWRy4tJqSUrerDFCyCe5DT6FUBa/8hJ0VyeJ2X5J+ni31FKBGWdCQ mWI35ZAw==; Received: from [2601:1c0:6280:3f0:897c:6038:c71d:ecac] by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9tuq-0007DD-EB; Thu, 05 Mar 2020 17:04:08 +0000 Subject: Re: mmotm 2020-03-03-22-28 uploaded (warning: objtool:) To: Peter Zijlstra , Walter Wu Cc: akpm@linux-foundation.org, broonie@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-next@vger.kernel.org, mhocko@suse.cz, mm-commits@vger.kernel.org, sfr@canb.auug.org.au, Josh Poimboeuf , dvyukov@google.com References: <20200304062843.9yA6NunM5%akpm@linux-foundation.org> <20200305081717.GT2596@hirez.programming.kicks-ass.net> <20200305081842.GB2619@hirez.programming.kicks-ass.net> <1583399782.17146.14.camel@mtksdccf07> <20200305095436.GV2596@hirez.programming.kicks-ass.net> From: Randy Dunlap Message-ID: Date: Thu, 5 Mar 2020 09:04:07 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200305095436.GV2596@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/5/20 1:54 AM, Peter Zijlstra wrote: > On Thu, Mar 05, 2020 at 05:16:22PM +0800, Walter Wu wrote: >> On Thu, 2020-03-05 at 09:18 +0100, Peter Zijlstra wrote: >>> On Thu, Mar 05, 2020 at 09:17:17AM +0100, Peter Zijlstra wrote: >>>> On Wed, Mar 04, 2020 at 09:34:49AM -0800, Randy Dunlap wrote: >>> >>>>> mm/kasan/common.o: warning: objtool: kasan_report()+0x13: call to report_enabled() with UACCESS enabled >>>> >>>> I used next/master instead, and found the below broken commit >>>> responsible for this. Yes, I see that same warning in linux-next of 20200305. >>>> @@ -634,12 +637,20 @@ void kasan_free_shadow(const struct vm_struct *vm) >>>> #endif >>>> >>>> extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); >>>> +extern bool report_enabled(void); >>>> >>>> -void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) >>>> +bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) >>>> { >>>> - unsigned long flags = user_access_save(); >>>> + unsigned long flags; >>>> + >>>> + if (likely(!report_enabled())) >>>> + return false; >>> >>> This adds an explicit call before the user_access_save() and that is a >>> straight on bug. >>> >> Hi Peter, >> >> Thanks for your help. Unfortunately, I don't reproduce it in our >> environment, so I have asked Stephen, if I can reproduce it, then we >> will send new patch. > > The patch is trivial; and all you need is an x86_64 (cross) compiler to > reproduce. > > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index ad2dc0c9cc17..2906358e42f0 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -618,16 +618,17 @@ extern bool report_enabled(void); > > bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) > { > - unsigned long flags; > + unsigned long flags = user_access_save(); > + bool ret = false; > > - if (likely(!report_enabled())) > - return false; > + if (likely(report_enabled())) { > + __kasan_report(addr, size, is_write, ip); > + ret = true; > + } > > - flags = user_access_save(); > - __kasan_report(addr, size, is_write, ip); > user_access_restore(flags); > > - return true; > + return ret; > } > > #ifdef CONFIG_MEMORY_HOTPLUG > and that fixes the warning. Thanks. Acked-by: Randy Dunlap # build-tested -- ~Randy