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 E2636C433F5 for ; Thu, 5 May 2022 15:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380969AbiEEPF5 (ORCPT ); Thu, 5 May 2022 11:05:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380949AbiEEPF4 (ORCPT ); Thu, 5 May 2022 11:05:56 -0400 Received: from us-smtp-delivery-74.mimecast.com (us-smtp-delivery-74.mimecast.com [170.10.129.74]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 73DCA222BD for ; Thu, 5 May 2022 08:02:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651762935; 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=I3fL/x7Xenik54basEds0J2F7uKxunsCuMprnbYoyPM=; b=NVBX972iFFolnrKC/n4Yc3N5vcFDro6HK4moQcTMZYO+RWSZAN8BeUBYsKAVNkfH97bcul YQU9j9DbEJbUvMhq5tEmr3AJ36U/hqS8ULraA6s6uV8sHQ77q+Fh/ARAL3MSeqt34gqJU3 Fa+vgeO8/y0xZKqWfIoeTelB/vaqKx4= 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-517-_OCgwZHFOa-R75Os49XEVg-1; Thu, 05 May 2022 11:02:09 -0400 X-MC-Unique: _OCgwZHFOa-R75Os49XEVg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CEADA1014A69; Thu, 5 May 2022 15:02:06 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.3]) by smtp.corp.redhat.com (Postfix) with SMTP id AD2C49E94; Thu, 5 May 2022 15:02:01 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 5 May 2022 17:02:05 +0200 (CEST) Date: Thu, 5 May 2022 17:01:59 +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 , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org Subject: Re: [PATCH v3 08/11] ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs Message-ID: <20220505150158.GB13929@redhat.com> References: <87k0b0apne.fsf_-_@email.froward.int.ebiederm.org> <20220504224058.476193-8-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220504224058.476193-8-ebiederm@xmission.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/04, Eric W. Biederman wrote: > > With the removal of the incomplete detection of the tracer going away > in ptrace_stop, ptrace_stop always sleeps in schedule after > ptrace_freeze_traced succeeds. Modify ptrace_check_attach to > warn if wait_task_inactive fails. Oh. Again, I don't understand the changelog. If we forget about RT, ptrace_stop() will always sleep if ptrace_freeze_traced() succeeds. may_ptrace_stop() has gone. IOW. Lets forget about RT > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -266,17 +266,9 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > } > read_unlock(&tasklist_lock); > > - if (!ret && !ignore_state) { > - if (!wait_task_inactive(child, __TASK_TRACED)) { > - /* > - * This can only happen if may_ptrace_stop() fails and > - * ptrace_stop() changes ->state back to TASK_RUNNING, > - * so we should not worry about leaking __TASK_TRACED. > - */ > - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED); > - ret = -ESRCH; > - } > - } > + if (!ret && !ignore_state && > + WARN_ON_ONCE(!wait_task_inactive(child, __TASK_TRACED))) > + ret = -ESRCH; > > return ret; > } Why do you think this change would be wrong without any other changes? Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-74.mimecast.com ([170.10.129.74]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nmczh-00GWsu-HG for linux-um@lists.infradead.org; Thu, 05 May 2022 15:02:18 +0000 Date: Thu, 5 May 2022 17:01:59 +0200 From: Oleg Nesterov Subject: Re: [PATCH v3 08/11] ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs Message-ID: <20220505150158.GB13929@redhat.com> References: <87k0b0apne.fsf_-_@email.froward.int.ebiederm.org> <20220504224058.476193-8-ebiederm@xmission.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220504224058.476193-8-ebiederm@xmission.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 , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org On 05/04, Eric W. Biederman wrote: > > With the removal of the incomplete detection of the tracer going away > in ptrace_stop, ptrace_stop always sleeps in schedule after > ptrace_freeze_traced succeeds. Modify ptrace_check_attach to > warn if wait_task_inactive fails. Oh. Again, I don't understand the changelog. If we forget about RT, ptrace_stop() will always sleep if ptrace_freeze_traced() succeeds. may_ptrace_stop() has gone. IOW. Lets forget about RT > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -266,17 +266,9 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > } > read_unlock(&tasklist_lock); > > - if (!ret && !ignore_state) { > - if (!wait_task_inactive(child, __TASK_TRACED)) { > - /* > - * This can only happen if may_ptrace_stop() fails and > - * ptrace_stop() changes ->state back to TASK_RUNNING, > - * so we should not worry about leaking __TASK_TRACED. > - */ > - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED); > - ret = -ESRCH; > - } > - } > + if (!ret && !ignore_state && > + WARN_ON_ONCE(!wait_task_inactive(child, __TASK_TRACED))) > + ret = -ESRCH; > > return ret; > } Why do you think this change would be wrong without any other changes? Oleg. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Date: Thu, 05 May 2022 15:01:59 +0000 Subject: Re: [PATCH v3 08/11] ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs Message-Id: <20220505150158.GB13929@redhat.com> List-Id: References: <87k0b0apne.fsf_-_@email.froward.int.ebiederm.org> <20220504224058.476193-8-ebiederm@xmission.com> In-Reply-To: <20220504224058.476193-8-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org On 05/04, Eric W. Biederman wrote: > > With the removal of the incomplete detection of the tracer going away > in ptrace_stop, ptrace_stop always sleeps in schedule after > ptrace_freeze_traced succeeds. Modify ptrace_check_attach to > warn if wait_task_inactive fails. Oh. Again, I don't understand the changelog. If we forget about RT, ptrace_stop() will always sleep if ptrace_freeze_traced() succeeds. may_ptrace_stop() has gone. IOW. Lets forget about RT > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -266,17 +266,9 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > } > read_unlock(&tasklist_lock); > > - if (!ret && !ignore_state) { > - if (!wait_task_inactive(child, __TASK_TRACED)) { > - /* > - * This can only happen if may_ptrace_stop() fails and > - * ptrace_stop() changes ->state back to TASK_RUNNING, > - * so we should not worry about leaking __TASK_TRACED. > - */ > - WARN_ON(READ_ONCE(child->__state) = __TASK_TRACED); > - ret = -ESRCH; > - } > - } > + if (!ret && !ignore_state && > + WARN_ON_ONCE(!wait_task_inactive(child, __TASK_TRACED))) > + ret = -ESRCH; > > return ret; > } Why do you think this change would be wrong without any other changes? Oleg.