From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752623AbdAUAdJ (ORCPT ); Fri, 20 Jan 2017 19:33:09 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:39474 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752244AbdAUAdH (ORCPT ); Fri, 20 Jan 2017 19:33:07 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Nikolay Borisov Cc: Dmitry Vyukov , avagin , serge@hallyn.com, Kees Cook , Al Viro , LKML , syzkaller References: <877f5py5c2.fsf@xmission.com> Date: Sat, 21 Jan 2017 13:28:09 +1300 In-Reply-To: (Nikolay Borisov's message of "Sat, 21 Jan 2017 00:44:24 +0200") Message-ID: <87lgu5w92e.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1cUjbO-00058L-Ky;;;mid=<87lgu5w92e.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=101.100.131.98;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19HPeTKa5uv+wk9alg/+QaGYkW3HN5sr24= X-SA-Exim-Connect-IP: 101.100.131.98 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Nikolay Borisov X-Spam-Relay-Country: X-Spam-Timing: total 439 ms - load_scoreonly_sql: 0.05 (0.0%), signal_user_changed: 3.3 (0.8%), b_tie_ro: 2.4 (0.5%), parse: 1.25 (0.3%), extract_message_metadata: 4.6 (1.0%), get_uri_detail_list: 1.95 (0.4%), tests_pri_-1000: 6 (1.4%), tests_pri_-950: 1.96 (0.4%), tests_pri_-900: 1.69 (0.4%), tests_pri_-400: 29 (6.6%), check_bayes: 27 (6.2%), b_tokenize: 10 (2.3%), b_tok_get_all: 7 (1.7%), b_comp_prob: 3.8 (0.9%), b_tok_touch_all: 2.7 (0.6%), b_finish: 0.85 (0.2%), tests_pri_0: 363 (82.7%), check_dkim_signature: 0.84 (0.2%), check_dkim_adsp: 4.4 (1.0%), tests_pri_500: 6 (1.4%), rewrite_mail: 0.00 (0.0%) Subject: Re: namespace: deadlock in dec_pid_namespaces X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nikolay Borisov writes: > On 20.01.2017 20:05, Eric W. Biederman wrote: >> Nikolay Borisov writes: >> >>> On 20.01.2017 15:07, Dmitry Vyukov wrote: >>>> Hello, >>>> >>>> I've got the following deadlock report while running syzkaller fuzzer >>>> on eec0d3d065bfcdf9cd5f56dd2a36b94d12d32297 of linux-next (on odroid >>>> device if it matters): >> >> I am puzzled I thought we had fixed this with: >> add7c65ca426 ("pid: fix lockdep deadlock warning due to ucount_lock") >> But apparently not. We just moved it from hardirq to softirq context. Bah. >> >> Thank you very much for the report. >> >> Nikolay can you make your change use spinlock_irq? And have put_ucounts >> do spin_lock_irqsave? That way we just don't care where we call this. > > Like the one attached? Exactly thank you. Dmitry if you have time to test that patch and verify it fixes your issue I would appreciate it. > I haven't really taken careful look as to whether > the function where _irq versions do fiddle with irq state, since this > might cause a problem if we unconditionally enable them. In code paths where we can sleep irqs must come in enabled or it's a bug. spin_lock_irq which unconditionally disables irqs is thus safe on the allocation path. Similary spin_unlock_irq which unconditionally enables irqs is also safe on the allocation path. Eric