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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,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 A8639C28CF6 for ; Fri, 3 Aug 2018 12:14:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A95421759 for ; Fri, 3 Aug 2018 12:14:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5A95421759 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728343AbeHCOKN (ORCPT ); Fri, 3 Aug 2018 10:10:13 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727464AbeHCOKN (ORCPT ); Fri, 3 Aug 2018 10:10:13 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6C4AA7DAC3; Fri, 3 Aug 2018 12:14:09 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 27DFB21565E1; Fri, 3 Aug 2018 12:14:07 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 3 Aug 2018 14:14:09 +0200 (CEST) Date: Fri, 3 Aug 2018 14:14:07 +0200 From: Oleg Nesterov To: =?iso-8859-1?Q?J=FCrg?= Billeter Cc: Andrew Morton , Thomas Gleixner , Eric Biederman , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] prctl: add PR_[GS]ET_KILLABLE Message-ID: <20180803121406.GB13794@redhat.com> References: <20180730075241.24002-1-j@bitron.ch> <20180731070337.61004-1-j@bitron.ch> <20180731143949.GA1890@redhat.com> <20180801141914.GA21248@redhat.com> <7f7c57230e0279f4599bf13ae1d1d449d76ac232.camel@bitron.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7f7c57230e0279f4599bf13ae1d1d449d76ac232.camel@bitron.ch> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Fri, 03 Aug 2018 12:14:09 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Fri, 03 Aug 2018 12:14:09 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'oleg@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03, Jürg Billeter wrote: > > On Wed, 2018-08-01 at 16:19 +0200, Oleg Nesterov wrote: > > On 07/31, Jürg Billeter wrote: > > > > > > > Could you explain your use-case? Why a shell wants to use > > > > CLONE_NEWPID? > > > > > > To guarantee that there won't be any runaway processes, i.e., ensure > > > that no descendants (background helper daemons or misbehaving > > > processes) survive when the child process is terminated. > > > > We already have PR_SET_CHILD_SUBREAPER. > > > > Perhaps we can finally add PR_KILL_MY_DESCENDANTS_ON_EXIT? This was already > > discussed some time ago, but I can't find the previous discussion... Simple > > to implement. > > This would definitely be an option. You mentioned it last October in > the PR_SET_PDEATHSIG_PROC discussion¹. However, as PID namespaces > already exist and appear to be a good fit for the most part, Sure, if CLONE_NEWPID fits your needs you can use it, > I think it > makes sense to just add the missing pieces to PID namespaces instead of > duplicating part of the PID namespace functionality. Again, I am not arguing with your change. PR_KILL_MY_DESCENDANTS_ON_EXIT can make sense just like PR_SET_CHILD_SUBREAPER even if PID namespace functionality implies both. Simply because CLONE_NEWPID is not necessarily the best tool, if nothing else you do not necessarily want the pid isolation. > Also, based on Eric's comment in that other discussion about > no_new_privs not being allowed to increase the attack surface, > PR_KILL_MY_DESCENDANTS_ON_EXIT might require CAP_SYS_ADMIN as well (due > to setuid children). No, no, the exiting parent should simply do group_send_sig_info(SIGKILL) for every descendant and rely on check_kill_permission(). OK, lets forget it for now. Oleg.