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 DB756C433EF for ; Wed, 27 Apr 2022 16:33:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243123AbiD0QhH (ORCPT ); Wed, 27 Apr 2022 12:37:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36904 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241617AbiD0QhD (ORCPT ); Wed, 27 Apr 2022 12:37:03 -0400 Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B5105EBC9; Wed, 27 Apr 2022 09:33:52 -0700 (PDT) Received: from in02.mta.xmission.com ([166.70.13.52]:59410) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njkbt-003CeB-6u; Wed, 27 Apr 2022 10:33:49 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:35922 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njkbs-00Bkn9-90; Wed, 27 Apr 2022 10:33:48 -0600 From: "Eric W. Biederman" To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, rjw@rjwysocki.net, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , inux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn In-Reply-To: <20220427160901.GI17421@redhat.com> (Oleg Nesterov's message of "Wed, 27 Apr 2022 18:09:03 +0200") References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-9-ebiederm@xmission.com> <20220427160901.GI17421@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) Date: Wed, 27 Apr 2022 11:33:40 -0500 Message-ID: <87o80m7afv.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1njkbs-00Bkn9-90;;;mid=<87o80m7afv.fsf@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=softfail X-XM-AID: U2FsdGVkX1/ERgJ97yOK665IszA6bR2ejt/teDKEMaQ= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 9/9] ptrace: Don't change __state X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 04/26, Eric W. Biederman wrote: >> >> @@ -253,7 +252,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) >> */ >> if (lock_task_sighand(child, &flags)) { >> if (child->ptrace && child->parent == current) { >> - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED); >> + WARN_ON(child->jobctl & JOBCTL_DELAY_WAKEKILL); > > This WARN_ON() doesn't look right. > > It is possible that this child was traced by another task and PTRACE_DETACH'ed, > but it didn't clear DELAY_WAKEKILL. That would be a bug. That would mean that PTRACE_DETACHED process can not be SIGKILL'd. > If the new debugger attaches and calls ptrace() before the child takes siglock > ptrace_freeze_traced() will fail, but we can hit this WARN_ON(). Eric