From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH v2] prctl: add PR_[GS]ET_KILLABLE Date: Fri, 3 Aug 2018 14:14:07 +0200 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-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <7f7c57230e0279f4599bf13ae1d1d449d76ac232.camel@bitron.ch> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-api@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.