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 4F7FEC433F5 for ; Wed, 27 Apr 2022 17:21:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244029AbiD0RYk (ORCPT ); Wed, 27 Apr 2022 13:24:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244037AbiD0RYi (ORCPT ); Wed, 27 Apr 2022 13:24:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4BF7145AE4 for ; Wed, 27 Apr 2022 10:21:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651080083; 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=MGbpkBAM5ckrE2XkacROVUw8iTojO8omojTbuiRlzq4=; b=ZjrALiIza1OEmkMI5mq57l/G5Enl4ervyIfK1ucuW60P2LpeBY8Vu9ZFMrgp1/l+ZuJAhW EoYyQcvQ/CbZug0FXRwcZkFHHh12CKvpy28+20FZoY06ysKrxXZ3Ek7kvW17YPOKZKKl8a XaeypmY1YZC9uwDC1NzJh/pqyoG07z8= 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-376-OGwoKz8ROxW-U8jIWnjSjw-1; Wed, 27 Apr 2022 13:21:17 -0400 X-MC-Unique: OGwoKz8ROxW-U8jIWnjSjw-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 89F1E88B7BC; Wed, 27 Apr 2022 17:21:16 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.128]) by smtp.corp.redhat.com (Postfix) with SMTP id 9A5582024CB6; Wed, 27 Apr 2022 17:21:11 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 27 Apr 2022 19:21:16 +0200 (CEST) Date: Wed, 27 Apr 2022 19:21:10 +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: <20220427172109.GK17421@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-9-ebiederm@xmission.com> <20220427160901.GI17421@redhat.com> <87o80m7afv.fsf@email.froward.int.ebiederm.org> <20220427171829.GJ17421@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220427171829.GJ17421@redhat.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 04/27, Oleg Nesterov wrote: > > On 04/27, Eric W. Biederman wrote: > > > > 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. > > Why? The tracee will take siglock, clear JOBCTL_DELAY_WAKEKILL and notice > SIGKILL after that. Not to mention that the tracee is TASK_RUNNING after PTRACE_DETACH wakes it up, so the pending JOBCTL_DELAY_WAKEKILL simply has no effect. Oleg. > > > 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 > > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1njlLs-002cgg-72 for linux-um@lists.infradead.org; Wed, 27 Apr 2022 17:21:21 +0000 Date: Wed, 27 Apr 2022 19:21:10 +0200 From: Oleg Nesterov Subject: Re: [PATCH 9/9] ptrace: Don't change __state Message-ID: <20220427172109.GK17421@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-9-ebiederm@xmission.com> <20220427160901.GI17421@redhat.com> <87o80m7afv.fsf@email.froward.int.ebiederm.org> <20220427171829.GJ17421@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220427171829.GJ17421@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org 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 On 04/27, Oleg Nesterov wrote: > > On 04/27, Eric W. Biederman wrote: > > > > 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. > > Why? The tracee will take siglock, clear JOBCTL_DELAY_WAKEKILL and notice > SIGKILL after that. Not to mention that the tracee is TASK_RUNNING after PTRACE_DETACH wakes it up, so the pending JOBCTL_DELAY_WAKEKILL simply has no effect. Oleg. > > > 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 > > _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um