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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 08E04C282CA for ; Wed, 13 Feb 2019 04:09:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D42FA222BB for ; Wed, 13 Feb 2019 04:09:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388527AbfBMEJZ (ORCPT ); Tue, 12 Feb 2019 23:09:25 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:55450 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388465AbfBMEJW (ORCPT ); Tue, 12 Feb 2019 23:09:22 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gtlrM-0006Kh-LC; Tue, 12 Feb 2019 21:09:20 -0700 Received: from ip68-227-174-240.om.om.cox.net ([68.227.174.240] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gtlrL-0000r9-P5; Tue, 12 Feb 2019 21:09:20 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Oleg Nesterov Cc: Dmitry Vyukov , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , LKML , Arnaldo Carvalho de Melo , Alexander Shishkin , jolsa@redhat.com, Namhyung Kim , luca abeni , syzkaller , Ivan Delalande References: <878syu7tcm.fsf@xmission.com> <87tvhi4vl7.fsf@xmission.com> <87o97q1cky.fsf_-_@xmission.com> <20190206180754.GA23476@redhat.com> <87imxwv9jp.fsf@xmission.com> <875ztwt7yy.fsf_-_@xmission.com> <87zhr8rtd6.fsf_-_@xmission.com> <20190211141340.GA21430@redhat.com> <87zhr1g7ls.fsf@xmission.com> <871s4dctci.fsf@xmission.com> <20190212165022.GA29263@redhat.com> Date: Tue, 12 Feb 2019 22:09:14 -0600 In-Reply-To: <20190212165022.GA29263@redhat.com> (Oleg Nesterov's message of "Tue, 12 Feb 2019 17:50:23 +0100") Message-ID: <87ef8c5nyt.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=1gtlrL-0000r9-P5;;;mid=<87ef8c5nyt.fsf_-_@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.240;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+iZIJ7cbRve7KlhsKCKfyDAnjWkSnbmLg= X-SA-Exim-Connect-IP: 68.227.174.240 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH] signal: Restore the stop PTRACE_EVENT_EXIT X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the middle of do_exit() there is there is a call "ptrace_event(PTRACE_EVENT_EXIT, code);" That call places the process in TACKED_TRACED aka "(TASK_WAKEKILL | __TASK_TRACED)" and waits for for the debugger to release the task or SIGKILL to be delivered. Skipping past dequeue_signal when we know a fatal signal has already been delivered resulted in SIGKILL remaining pending and TIF_SIGPENDING remaining set. This in turn caused the scheduler to not sleep in PTACE_EVENT_EXIT as it figured a fatal signal was pending. This also caused ptrace_freeze_traced in ptrace_check_attach to fail because it left a per thread SIGKILL pending which is what fatal_signal_pending tests for. This difference in signal state caused strace to report strace: Exit of unknown pid NNNNN ignored Therefore update the signal handling state like dequeue_signal would when removing a per thread SIGKILL, by removing SIGKILL from the per thread signal mask and clearing TIF_SIGPENDING. Reported-by: Oleg Nesterov Reported-by: Ivan Delalande Cc: stable@vger.kernel.org Fixes: 35634ffa1751 ("signal: Always notice exiting tasks") Signed-off-by: "Eric W. Biederman" --- Ivan this change fixes the issues you reported to me. Can you confirm? Oleg this looks like the most conservative regression fix I can manage. kernel/signal.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 99fa8ff06fd9..57b7771e20d7 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2436,9 +2436,12 @@ bool get_signal(struct ksignal *ksig) } /* Has this task already been marked for death? */ - ksig->info.si_signo = signr = SIGKILL; - if (signal_group_exit(signal)) + if (signal_group_exit(signal)) { + ksig->info.si_signo = signr = SIGKILL; + sigdelset(¤t->pending.signal, SIGKILL); + recalc_sigpending(); goto fatal; + } for (;;) { struct k_sigaction *ka; -- 2.17.1