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 X-Spam-Level: X-Spam-Status: No, score=-4.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66283C43387 for ; Wed, 2 Jan 2019 21:17:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B70A2075B for ; Wed, 2 Jan 2019 21:17:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="h943bmeQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728645AbfABVRY (ORCPT ); Wed, 2 Jan 2019 16:17:24 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:45276 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726089AbfABVRY (ORCPT ); Wed, 2 Jan 2019 16:17:24 -0500 Received: by mail-pl1-f193.google.com with SMTP id a14so14968086plm.12 for ; Wed, 02 Jan 2019 13:17:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=NJ2oVcbQ92As/PIuIVMLD9oLARFady9J9+58udv/F9s=; b=h943bmeQon7Sv9WNXM9IZ7b8ofhiDHxJK3JTtDrpzex9Z48P+q1MEbQ4Mz8NVRAOmz SV9bYn9hXOYJ/kNpu0AlpgeOoJlLde9hMIuKa6YKaFBB33D+AiydEpun73aKIDS7Sowe ElobUHbQMgyOwKfxOF94cGbcsdv2mznJx7EBjSkPS2JI1IWUvZ5V8RDWzZ1y/RX5AdWo /tbOsnZz+XiYIM0T7Pnt92HT5a2eyYvkYIja8h3F6Aaa2Tv5lgssrlwL8FWdI8fi0m75 NEOODV5RsGggnfpMLv/LMso0DqkarY5VDArkrp1rjmfUMZeKinYIYl0LTAahu337+Xid AJGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=NJ2oVcbQ92As/PIuIVMLD9oLARFady9J9+58udv/F9s=; b=fGLN+cctz+e7GHgXulG6mGBRSCB6E2PAOO4JReWTOjq4sVM3GnXawqueFnYu5lxODJ LohssKTfy25hWZ+hIfFB2TXzH33JDlj/eDKhPhhdlfcqLqt8zel3yHL/fQ6w/A7cc3mc o31Huyly9p1UlTHrrScgSrODh6suSLSA/jt0+Ui6A0SEpgExr2pscWwf/0W/iN2+RL7T kEelomjbMgQs29xRLhBL0HgVHPCxDJk86HGkxkkmNC5o0Gh+WOvJEqyIjLxqFPjQw1BZ MWLMXJNAf2ejWzUoJYbMqAo/r7HGAabk+v/IvbLNZyXpfPFg+AfElXYnA4rQjuaefxDn 95ZQ== X-Gm-Message-State: AJcUukeT5n71x/BVBoXc0yzUtY1msF/4zHkLSM0ccvUFOqLaMuyG6fEf 09qgnS7scdVUHOo5RqI29To6v/XA X-Google-Smtp-Source: ALg8bN5URL8Qp0ACfl7gqTSBEc9vKT4PHu/6/iqbZWLCqDyCPsq1TVBpSm06swyY7fX71zcTd/7lmA== X-Received: by 2002:a17:902:bb86:: with SMTP id m6mr45417920pls.315.1546463843677; Wed, 02 Jan 2019 13:17:23 -0800 (PST) Received: from gmail.com ([2620:0:1008:fd00:78b4:3a07:980a:287b]) by smtp.gmail.com with ESMTPSA id a18sm71540510pgj.30.2019.01.02.13.17.22 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 02 Jan 2019 13:17:23 -0800 (PST) Date: Wed, 2 Jan 2019 13:17:21 -0800 From: Andrei Vagin To: Alexander Viro , Andrew Morton , Oleg Nesterov Cc: linux-kernel@vger.kernel.org, "Eric W. Biederman" Subject: Re: [PATCH] kernel: release ptraced tasks before zap_pid_ns_processes Message-ID: <20190102211720.GB3237@gmail.com> References: <20190102205939.26231-1-avagin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20190102205939.26231-1-avagin@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oops, Al is here by mistake. Sorry about that. On Wed, Jan 02, 2019 at 12:59:39PM -0800, Andrei Vagin wrote: > Currently, exit_ptrace() adds all ptraced tasks in a dead list, than > zap_pid_ns_processes() waits all tasks in a current pid ns, and only > then tasks from the dead list are released. > > zap_pid_ns_processes() can stuck on waiting tasks from the dead list. In > this case, we will have one unkillable process with one or more dead > children. > > Cc: Oleg Nesterov > Cc: "Eric W. Biederman" > Cc: Andrew Morton > Signed-off-by: Andrei Vagin > --- > kernel/exit.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/kernel/exit.c b/kernel/exit.c > index 0e21e6d21f35..ccaa6f6549ba 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -664,9 +664,6 @@ static void forget_original_parent(struct task_struct *father, > { > struct task_struct *p, *t, *reaper; > > - if (unlikely(!list_empty(&father->ptraced))) > - exit_ptrace(father, dead); > - > /* Can drop and reacquire tasklist_lock */ > reaper = find_child_reaper(father); > if (list_empty(&father->children)) > @@ -705,8 +702,18 @@ static void exit_notify(struct task_struct *tsk, int group_dead) > LIST_HEAD(dead); > > write_lock_irq(&tasklist_lock); > - forget_original_parent(tsk, &dead); > + if (unlikely(!list_empty(&tsk->ptraced))) > + exit_ptrace(tsk, &dead); > + write_unlock_irq(&tasklist_lock); > + > + /* Ptraced tasks have to be released before zap_pid_ns_processes(). */ > + list_for_each_entry_safe(p, n, &dead, ptrace_entry) { > + list_del_init(&p->ptrace_entry); > + release_task(p); > + } > > + write_lock_irq(&tasklist_lock); > + forget_original_parent(tsk, &dead); > if (group_dead) > kill_orphaned_pgrp(tsk->group_leader, NULL); > > -- > 2.17.2 >