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=-10.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 5C2E1C1B0D8 for ; Wed, 16 Dec 2020 21:47:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 088AA236FB for ; Wed, 16 Dec 2020 21:47:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726523AbgLPVrX (ORCPT ); Wed, 16 Dec 2020 16:47:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726841AbgLPVrX (ORCPT ); Wed, 16 Dec 2020 16:47:23 -0500 Received: from mail-pg1-x535.google.com (mail-pg1-x535.google.com [IPv6:2607:f8b0:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71260C0617A7 for ; Wed, 16 Dec 2020 13:46:43 -0800 (PST) Received: by mail-pg1-x535.google.com with SMTP id t37so18565557pga.7 for ; Wed, 16 Dec 2020 13:46:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=poAfl3bDtaKUASJKI462JFGUU+Oc+LFF2NNC85CJWOs=; b=cUrJuCCxp683ndejeLrG8EY4QEXqHn1D7H2UlO8fDFZ9zX1V+2NP+bpkE3eMHPK9Ua vsdNg8TcwoY9Xg2PAt/Agf1nBtcE79ImF54f7AZYGxhqTNiBRQagFkSe9xxNT9insXjW c0+neWxgAIJKsLdLzTgzQq2VZVa+YsNZRts4g3GW0Y7vPDalLqMTZwtfi7DHb3LUpEyd FTLzZ2w4cm+9TrIXQD49Ipw7IgUgEk3QTM7+E2D4OWV42MKOo5qJn/Oq6QIj4ZHeTy7l yYiHjS9synQe+vou1FAfz9iZtQYGaWS92JQvilf2i2NhqitKlvaT906gEE9TmOWn4cOF HAYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=poAfl3bDtaKUASJKI462JFGUU+Oc+LFF2NNC85CJWOs=; b=J1WqFwcv72O3wOtbZ9QoLIPS0M6K+HVwGHB53P+Xu9YFEmKYS4fKkvc4TI8j6qZBMI q4eZu2AV09XlkjfTwEuy1IPA6n7es72ugmpgo5l4w4uSNn3vwUPNCMQp6lbDtsxpxmAZ 1PXdReo6jVQ8Zr9hw4mttulGLs4d6Gm6kzpyPuaQbSbpL3iv83Ms716h1vsMyUl4pUmi yVXDFPwLZCt5/Bx3zJ1E4FG61m45sHwthcfEUIQEXITwxBiGGCi1156UV/0306X1pVOT 5mQtiqXzHBbROrql+ajc+MEbBfefzCnQ3tvduw4nmUUvI5qj7s/rH6xo2UsZ8pnl+jkh geiA== X-Gm-Message-State: AOAM5312Bdztb0px6K/MZBBomwFgnu7H8znz0WhTyvOX0i814uAi1OT4 o66RJdX8avp6Vldr/Iyy4N2i/A== X-Google-Smtp-Source: ABdhPJyk+DxUhJXC3y13LsRvsNxQHhpA2c6l0EwRpLeGeBGLCQIUF91JfFWlkZVg68d0q7IlikPW7A== X-Received: by 2002:a62:1e81:0:b029:19e:2121:2df1 with SMTP id e123-20020a621e810000b029019e21212df1mr34214209pfe.1.1608155202845; Wed, 16 Dec 2020 13:46:42 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id f24sm2969668pjj.5.2020.12.16.13.46.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Dec 2020 13:46:42 -0800 (PST) Subject: Re: WARNING in percpu_ref_kill_and_confirm (2) To: syzbot , io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@kernel.org, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, will@kernel.org, Tejun Heo References: <0000000000004d454d05b69b5bd3@google.com> From: Jens Axboe Message-ID: <8694934b-7ac6-a29f-0126-4a311bea4c35@kernel.dk> Date: Wed, 16 Dec 2020 14:46:38 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <0000000000004d454d05b69b5bd3@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 12/16/20 2:14 PM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 7b1b868e Merge tag 'for-linus' of git://git.kernel.org/pub.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1156046b500000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3416bb960d5c705d > dashboard link: https://syzkaller.appspot.com/bug?extid=c9937dfb2303a5f18640 > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1407c287500000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10ed5f07500000 > > The issue was bisected to: > > commit 4d004099a668c41522242aa146a38cc4eb59cb1e > Author: Peter Zijlstra > Date: Fri Oct 2 09:04:21 2020 +0000 > > lockdep: Fix lockdep recursion Ehhh no... This is timing dependent, so probably why it ends up pinpointing something totally unrelated. > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14e9d433500000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=16e9d433500000 > console output: https://syzkaller.appspot.com/x/log.txt?x=12e9d433500000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+c9937dfb2303a5f18640@syzkaller.appspotmail.com > Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion") > > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441309 > RDX: 0000000000000002 RSI: 00000000200000c0 RDI: 0000000000003ad1 > RBP: 000000000000f2ae R08: 0000000000000002 R09: 00000000004002c8 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004021d0 > R13: 0000000000402260 R14: 0000000000000000 R15: 0000000000000000 > ------------[ cut here ]------------ > percpu_ref_kill_and_confirm called more than once on io_ring_ctx_ref_free! > WARNING: CPU: 0 PID: 8476 at lib/percpu-refcount.c:382 percpu_ref_kill_and_confirm+0x126/0x180 lib/percpu-refcount.c:382 > Modules linked in: > CPU: 0 PID: 8476 Comm: syz-executor389 Not tainted 5.10.0-rc7-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > RIP: 0010:percpu_ref_kill_and_confirm+0x126/0x180 lib/percpu-refcount.c:382 > Code: 5d 08 48 8d 7b 08 48 89 fa 48 c1 ea 03 80 3c 02 00 75 5d 48 8b 53 08 48 c7 c6 00 4b 9d 89 48 c7 c7 60 4a 9d 89 e8 c6 97 f6 04 <0f> 0b 48 b8 00 00 00 00 00 fc ff df 48 89 ea 48 c1 ea 03 80 3c 02 > RSP: 0018:ffffc9000b94fe10 EFLAGS: 00010086 > RAX: 0000000000000000 RBX: ffff888011da4580 RCX: 0000000000000000 > RDX: ffff88801fe84ec0 RSI: ffffffff8158c835 RDI: fffff52001729fb4 > RBP: ffff88801539f000 R08: 0000000000000001 R09: ffff8880b9e2011b > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000293 > R13: 0000000000000000 R14: 0000000000000000 R15: ffff88802de28758 > FS: 00000000014ab880(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f2a7046b000 CR3: 0000000023368000 CR4: 0000000000350ef0 > Call Trace: > percpu_ref_kill include/linux/percpu-refcount.h:149 [inline] > io_ring_ctx_wait_and_kill+0x2b/0x450 fs/io_uring.c:8382 > io_uring_release+0x3e/0x50 fs/io_uring.c:8420 > __fput+0x285/0x920 fs/file_table.c:281 > task_work_run+0xdd/0x190 kernel/task_work.c:151 > tracehook_notify_resume include/linux/tracehook.h:188 [inline] > exit_to_user_mode_loop kernel/entry/common.c:164 [inline] > exit_to_user_mode_prepare+0x17e/0x1a0 kernel/entry/common.c:191 > syscall_exit_to_user_mode+0x38/0x260 kernel/entry/common.c:266 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x441309 > Code: e8 5c ae 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007ffed6545d38 EFLAGS: 00000246 ORIG_RAX: 00000000000001a9 > RAX: fffffffffffffff4 RBX: 0000000000000000 RCX: 0000000000441309 > RDX: 0000000000000002 RSI: 00000000200000c0 RDI: 0000000000003ad1 > RBP: 000000000000f2ae R08: 0000000000000002 R09: 00000000004002c8 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004021d0 > R13: 0000000000402260 R14: 0000000000000000 R15: 0000000000000000 What I think happens here is that we switch mode, but exit before it's done. Wonder if there's a wait to wait for that on exit. Tejun? -- Jens Axboe