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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,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 1FC98C433DB for ; Wed, 31 Mar 2021 07:33:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCE7C619DC for ; Wed, 31 Mar 2021 07:33:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233720AbhCaHcv (ORCPT ); Wed, 31 Mar 2021 03:32:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234100AbhCaHcW (ORCPT ); Wed, 31 Mar 2021 03:32:22 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 153C7C061574 for ; Wed, 31 Mar 2021 00:32:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=dkzu4DMt6FWa6R1PXgA2donJuIwD/gU2RVBrtv9nBm8=; b=AJ17EukJxEHAPJnU8pTMCx5og9 1uaKR9zz8RZNGUewMeRVMiPTvSzED+YXIPV1lKNUvEsdww+xYt1fuU1+JathXlOAX9wedA3r1vAEx 43UPZMdZjHot0mUXQwe/c1qOVJRAyI8zLHZBE1HuJx5tTmfLRhvbXPXDI5UZXimlShYdxa8gAXG1d Xho1MNfeLjcYMw7v17x1wTgjoYvgP7SYrkTH4qVW6vNSiHLkd50XIu8IGnFszUZnd+8mYAqaEWX8f JOr9ykgMbthAejTEwvB8KuX7x9mvPQBvG96CdkqF3KN5Td6MPZNFs6tNrGTFw/A0bZxww947GjOQM hUFCUqJg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lRVJH-004Bqy-TE; Wed, 31 Mar 2021 07:30:45 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7E7D830015A; Wed, 31 Mar 2021 09:30:38 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5FE882B85BA0B; Wed, 31 Mar 2021 09:30:38 +0200 (CEST) Date: Wed, 31 Mar 2021 09:30:38 +0200 From: Peter Zijlstra To: Dmitry Vyukov Cc: syzbot , Ingo Molnar , Will Deacon , Andrew Morton , Jens Axboe , Christian Brauner , LKML , Shakeel Butt , syzkaller-bugs Subject: Re: [syzbot] WARNING: suspicious RCU usage in copy_page_range Message-ID: References: <00000000000086695705bec87c9f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 31, 2021 at 08:11:38AM +0200, Dmitry Vyukov wrote: > On Wed, Mar 31, 2021 at 12:26 AM syzbot > wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: db24726b Merge tag 'integrity-v5.12-fix' of git://git.kern.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=16c16b7cd00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=daeff30c2474a60f > > dashboard link: https://syzkaller.appspot.com/bug?extid=1a33233ccd8201ec2322 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+1a33233ccd8201ec2322@syzkaller.appspotmail.com > > I think this is a LOCKDEP issue. +LOCKDEP maintainers. > > Another bug happened on another thread ("WARNING: possible circular > locking dependency detected"). Lockdep disabled lock tracking > ("debug_locks = 0" in the report), which probably made it miss > rcu_unlock somewhere, but it did not turn off reporting yet and > produced the false positive first. > > I think if LOCKDEP disables lock tracking, it must also disable > reporting of issues that require lock tracking. That would avoid false > positives. Still early and brain hasn't really booted yet, but features that require lock tracking are supposed to check debug_locks. And afaict debug_lockdep_rcu_enabled(), which is called by RCU_LOCKDEP_WARN(), which is called by rcu_sleep_check() does just that.