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 4725CC433EF for ; Wed, 27 Apr 2022 14:57:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235360AbiD0PAM (ORCPT ); Wed, 27 Apr 2022 11:00:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239034AbiD0PAL (ORCPT ); Wed, 27 Apr 2022 11:00:11 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 22F867C175 for ; Wed, 27 Apr 2022 07:57:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651071419; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ntMBAFtwiC9qpWMmFF/p+IGii2jJjeJe+SyCWkAlVJI=; b=D971mpPD6vy0jZs8Fl9IRi8kcsTkn1yVBPz6+76ccjRRlqiZoxEp9Q3s3BMnsVakrp61FW lFRNtuRCCULW7jgETFhnTiatN95S9E53+zALwqtZFl0uxpvBqtlWblx6XHU/vx0QtlAtcC BuW236Ncf5ufUHKhGjFwRKUD9nKK958= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-643-oLs-316kMymZlYXURsAZcw-1; Wed, 27 Apr 2022 10:56:55 -0400 X-MC-Unique: oLs-316kMymZlYXURsAZcw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C53CF8039D7; Wed, 27 Apr 2022 14:56:54 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.128]) by smtp.corp.redhat.com (Postfix) with SMTP id D07F714A5061; Wed, 27 Apr 2022 14:56:48 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 27 Apr 2022 16:56:54 +0200 (CEST) Date: Wed, 27 Apr 2022 16:56:47 +0200 From: Oleg Nesterov To: "Eric W. Biederman" 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 Subject: Re: [PATCH 6/9] signal: Always call do_notify_parent_cldstop with siglock held Message-ID: <20220427145646.GC17421@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-6-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220426225211.308418-6-ebiederm@xmission.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 04/26, Eric W. Biederman wrote: > > @@ -2209,6 +2213,34 @@ static int ptrace_stop(int exit_code, int why, int clear_code, > spin_lock_irq(¤t->sighand->siglock); > } > > + /* Don't stop if current is not ptraced */ > + if (unlikely(!current->ptrace)) > + return (clear_code) ? 0 : exit_code; > + > + /* > + * If @why is CLD_STOPPED, we're trapping to participate in a group > + * stop. Do the bookkeeping. Note that if SIGCONT was delievered > + * across siglock relocks since INTERRUPT was scheduled, PENDING > + * could be clear now. We act as if SIGCONT is received after > + * TASK_TRACED is entered - ignore it. > + */ > + if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING)) > + gstop_done = task_participate_group_stop(current); > + > + /* > + * Notify parents of the stop. > + * > + * While ptraced, there are two parents - the ptracer and > + * the real_parent of the group_leader. The ptracer should > + * know about every stop while the real parent is only > + * interested in the completion of group stop. The states > + * for the two don't interact with each other. Notify > + * separately unless they're gonna be duplicates. > + */ > + do_notify_parent_cldstop(current, true, why); > + if (gstop_done && ptrace_reparented(current)) > + do_notify_parent_cldstop(current, false, why); This doesn't look right too. The parent should be notified only after we set __state = TASK_TRACED and ->exit code. Suppose that debugger sleeps in do_wait(). do_notify_parent_cldstop() wakes it up, debugger calls wait_task_stopped() and then it will sleep again, task_stopped_code() returns 0. This can be probably fixed if you remove the lockless (fast path) task_stopped_code() check in wait_task_stopped(), but this is not nice performance-wise... Oleg.