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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47565C433EF for ; Tue, 28 Dec 2021 11:26:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229653AbhL1L0c (ORCPT ); Tue, 28 Dec 2021 06:26:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229490AbhL1L0b (ORCPT ); Tue, 28 Dec 2021 06:26:31 -0500 Received: from mail-wr1-x431.google.com (mail-wr1-x431.google.com [IPv6:2a00:1450:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79869C061574; Tue, 28 Dec 2021 03:26:31 -0800 (PST) Received: by mail-wr1-x431.google.com with SMTP id a9so37692126wrr.8; Tue, 28 Dec 2021 03:26:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=OKkueDwCwEF+cqPVoTURbXkr2Ps39czU8l1nd/tBauI=; b=S7UiqpAigrV/OO8Qr159GCBG27b7VonKIbjlvQ0H/VkuUJhQ9iuOpDSiC/arydO3XJ 02Efj8RZ7FirsvLNwwe+62DWzTpE7lJlvK8G1qS4CAJDMMLdXuotwWi/8UtEPsUmp1Nr WxccogvNbQnS6dTgePAAzWi/e4a60VxOGHt7bFdbKJa6+lMMQib6y+oPwV2ZWWmdqL/l p5pGW7na1DgkDXKWWwObItmERJDbk4Rkxz2va/YKnribdiZHIcOUFhM1Zb6YRW3QfkMI YMU7b1QxTh+N57c642G1FtkNHKp9TQSXSQWVnmTSKmMyrkOnbDCknc/v91/m49ccJ1nf Bp5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=OKkueDwCwEF+cqPVoTURbXkr2Ps39czU8l1nd/tBauI=; b=Nq4EzUnBxmqTDSfFzux4BxQ2Lyt32N8Nzldu44KFVqA+9kSuOtGMnr4kMhralD2Noe Bl4NZT65bbV49uQTahitl1hIJWdkpJRT9AdLEOfn/qraCnzkQWaOjt02q8CAR4OnylEU 2NTlQSpS02WwQGBHgZ0Bcvyi1k3IEYI8wS3GpPAKjOIvUcGXa2pqCfdHN66BxHuWANYF z9gF5DbBzAnMjRlq+MK0eOf23N0UqcntS0Go9SB/rq3GNNsDxP0DaYpHhE4qfd34420x TMCpFh9l4DOuHz7HfHCtvQr8EK2nckAAB+YjWNS3xid5gHorRrwZ7daQxI8iFCzGZhqM d7CA== X-Gm-Message-State: AOAM530jFFHEmWQmGUTJ8cTfU0Oo15kingmWhK2NgrIymKhz55/q4Ni6 OrcRuWw4Z4JI2LrWD5I4888= X-Google-Smtp-Source: ABdhPJw9WReDcdp9vGFm+WMi0sI9xKTeumWkHdL06/dGDZKguTbonGLcSFSZfptU12FAghZrJBYd+g== X-Received: by 2002:a5d:64cc:: with SMTP id f12mr15934549wri.145.1640690790066; Tue, 28 Dec 2021 03:26:30 -0800 (PST) Received: from [192.168.8.198] ([148.252.128.140]) by smtp.gmail.com with ESMTPSA id m17sm22195431wmq.31.2021.12.28.03.26.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Dec 2021 03:26:29 -0800 (PST) Message-ID: <303f7772-eb31-5beb-2bd0-4278566591b0@gmail.com> Date: Tue, 28 Dec 2021 11:24:56 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL Content-Language: en-US To: "Eric W. Biederman" Cc: Olivier Langlois , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Alexander Viro , Jens Axboe , Oleg Nesterov , Linus Torvalds References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.fsf_-_@disp2133> <1b519092-2ebf-3800-306d-c354c24a9ad1@gmail.com> <13250a8d-1a59-4b7b-92e4-1231d73cbdda@gmail.com> <878rw9u6fb.fsf@email.froward.int.ebiederm.org> From: Pavel Begunkov In-Reply-To: <878rw9u6fb.fsf@email.froward.int.ebiederm.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 12/24/21 19:52, Eric W. Biederman wrote: > Pavel Begunkov writes: [...] >> FWIW, I worked it around in io_uring back then by breaking the >> dependency. > > I am in the middle of untangling the dependencies between ptrace, > coredump, signal handling and maybe a few related things. Sounds great > Do folks have a reproducer I can look at? Pavel especially if you have > something that reproduces on the current kernels. A syz reproducer was triggering it reliably, I'd try to revert the commit below and test: https://syzkaller.appspot.com/text?tag=ReproC&x=15d3600cb00000 It should hung a task. Syzbot report for reference: https://syzkaller.appspot.com/bug?extid=27d62ee6f256b186883e commit 1d5f5ea7cb7d15b9fb1cc82673ebb054f02cd7d2 Author: Pavel Begunkov Date: Fri Oct 29 13:11:33 2021 +0100 io-wq: remove worker to owner tw dependency INFO: task iou-wrk-6609:6612 blocked for more than 143 seconds. Not tainted 5.15.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:iou-wrk-6609 state:D stack:27944 pid: 6612 ppid: 6526 flags:0x00004006 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0xb44/0x5960 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0x176/0x280 kernel/sched/completion.c:138 io_worker_exit fs/io-wq.c:183 [inline] io_wqe_worker+0x66d/0xc40 fs/io-wq.c:597 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 ... > As part of that I am in the process of guaranteeing all of the coredump > work happens in get_signal so nothing of io_uring or any cleanup > anywhere else runs until the coredump completes. > > I haven't quite posted the code for review because it's the holidays. > But I am aiming at v5.17 or possibly v5.18, as the code is just about > ready. -- Pavel Begunkov