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 C2E2BC433EF for ; Wed, 27 Apr 2022 16:14:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242483AbiD0QRz (ORCPT ); Wed, 27 Apr 2022 12:17:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243947AbiD0QPm (ORCPT ); Wed, 27 Apr 2022 12:15:42 -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 581FA3BD079 for ; Wed, 27 Apr 2022 09:11:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651075756; 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=q/SkBNsoTUPyKMGhRFoyh0ykNNAvugZJ3bBfN9M/MEU=; b=PyGhNwXGadN2LpgTJBvTwUgqz7RBix+aUDcfwcNRQYEs2bEJjwE4SLcJzJa60XAdobO5zy dL8t9Zt1207X6+/fwm16om4ZYQXPxqa0jmuay6B1rGD0WgCu/Z9blI5bplgaakrmUIYLl6 9HLypceRWYDjC7CIoDgz84sbEEsXyz0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-381-fIC6HcHzNF2SRSCXM6IoTQ-1; Wed, 27 Apr 2022 12:09:10 -0400 X-MC-Unique: fIC6HcHzNF2SRSCXM6IoTQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 36B103820F6E; Wed, 27 Apr 2022 16:09:09 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.128]) by smtp.corp.redhat.com (Postfix) with SMTP id 45EE62024CB8; Wed, 27 Apr 2022 16:09:04 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 27 Apr 2022 18:09:08 +0200 (CEST) Date: Wed, 27 Apr 2022 18:09:03 +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 9/9] ptrace: Don't change __state Message-ID: <20220427160901.GI17421@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-9-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220426225211.308418-9-ebiederm@xmission.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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(). Oleg.