From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753871AbcGHGOk (ORCPT ); Fri, 8 Jul 2016 02:14:40 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:50234 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750985AbcGHGOb (ORCPT ); Fri, 8 Jul 2016 02:14:31 -0400 Message-ID: <1467958047.2322.110.camel@HansenPartnership.com> Subject: Re: [CRIU] Introspecting userns relationships to other namespaces? From: James Bottomley To: Andrei Vagin Cc: Andrew Vagin , "criu@openvz.org" , Linux API , Containers , lkml , Michael Kerrisk-manpages Date: Thu, 07 Jul 2016 23:07:27 -0700 In-Reply-To: References: <87r3b7pxja.fsf@x220.int.ebiederm.org> <20160706141348.GB20728@mail.hallyn.com> <20160707133631.GA2994@mail.hallyn.com> <1467903712.2347.16.camel@HansenPartnership.com> <1467919055.2322.36.camel@HansenPartnership.com> <20160708021617.GB10512@outlook.office365.com> <20160708030055.GC10512@outlook.office365.com> <1467948407.2322.88.camel@HansenPartnership.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2016-07-07 at 22:41 -0700, Andrei Vagin wrote: > On Thu, Jul 7, 2016 at 8:26 PM, James Bottomley > wrote: > > On Thu, 2016-07-07 at 20:00 -0700, Andrew Vagin wrote: > > > On Thu, Jul 07, 2016 at 07:16:18PM -0700, Andrew Vagin wrote: > > > > On Thu, Jul 07, 2016 at 12:17:35PM -0700, James Bottomley > > > > wrote: > > > > > On Thu, 2016-07-07 at 20:21 +0200, Michael Kerrisk (man > > > > > -pages) > > > > > wrote: > > > > > > On 7 July 2016 at 17:01, James Bottomley > > > > > > wrote: > > > > > [Serge already answered the parenting issue] > > > > > > > On Thu, 2016-07-07 at 08:36 -0500, Serge E. Hallyn wrote: > > > > > > > > Hm. Probably best-effort based on the process > > > > > > > > hierarchy. > > > > > > > > So > > > > > > > > yeah you could probably get a tree into a state that > > > > > > > > would > > > > > > > > be > > > > > > > > wrongly recreated. Create a new netns, bind mount it, > > > > > > > > exit; > > > > > > > > Have > > > > > > > > another task create a new user_ns, bind mount it, exit; > > > > > > > > Third > > > > > > > > task setns()s first to the new netns then to the new > > > > > > > > user_ns. I > > > > > > > > suspect criu will recreate that wrongly. > > > > > > > > > > > > > > This is a bit pathological, and you have to be root to do > > > > > > > it: > > > > > > > so > > > > > > > root can set up a nesting hierarchy, bind it and destroy > > > > > > > the > > > > > > > pids > > > > > > > but I know of no current orchestration system which does > > > > > > > this. > > > > > > > > > > > > > > Actually, I have to back pedal a bit: the way I currently > > > > > > > set > > > > > > > up > > > > > > > architecture emulation containers does precisely this: I > > > > > > > set > > > > > > > up the > > > > > > > namespaces unprivileged with child mount namespaces, but > > > > > > > then > > > > > > > I ask > > > > > > > root to bind the userns and kill the process that created > > > > > > > it > > > > > > > so I > > > > > > > have a permanent handle to enter the namespace by, so I > > > > > > > suspect > > > > > > > that when our current orchestration systems get more > > > > > > > sophisticated, > > > > > > > they might eventually want to do something like this as > > > > > > > well. > > > > > > > > > > > > > > In theory, we could get nsfs to show this information as > > > > > > > an > > > > > > > option > > > > > > > (just add a show_options entry to the superblock ops), > > > > > > > but > > > > > > > the > > > > > > > problem is that although each namespace has a parent > > > > > > > user_ns, > > > > > > > there's no way to get it without digging in the namespace > > > > > > > specific > > > > > > > structure. Probably we should restructure to move it > > > > > > > into > > > > > > > ns_common, then we could display it (and enforce all > > > > > > > namespaces > > > > > > > having owning user_ns) but it would be a > > > > > > > > > > > > I'm missing something here. Is it not already the case that > > > > > > all > > > > > > namespaces have an owning user_ns? > > > > > > > > > > Um, yes, I don't believe I said they don't. The problem I > > > > > thought you > > > > > were having is that there's no way of seeing what it is. > > > > > > > > > > nsfs is the Namespace fileystem where bound namespaces appear > > > > > to > > > > > a cat > > > > > of /proc/self/mounts. It can display any information that's > > > > > in > > > > > ns_common (the common core of namespaces) but the owning > > > > > user_ns > > > > > pointer currently isn't in this structure. Every user > > > > > namespace > > > > > has a > > > > > pointer to it, but they're all privately embedded in the > > > > > individual > > > > > namespace specific structures. What I was proposing was that > > > > > since > > > > > every current namespace has a pointer somewhere to the owning > > > > > user > > > > > namespace, we could abstract this out into ns_common so it's > > > > > now > > > > > accessible to be displayed by nsfs, probably as a mount > > > > > option. > > > > > > > > James, I am not sure that I understood you correctly. We have > > > > one > > > > file system for all namespace files, how we can show per-file > > > > properties > > > > in mount options. I think we can show all required information > > > > in > > > > fdinfo. We open a namespaces file (/proc/pid/ns/N) and then > > > > read > > > > /proc/pid/fdinfo/X for it. > > > > > > Here is a proof-of-concept patch. > > > > > > How it works: > > > > > > In [1]: import os > > > > > > In [2]: fd = os.open("/proc/self/ns/pid", os.O_RDONLY) > > > > > > In [3]: print open("/proc/self/fdinfo/%d" % fd).read() > > > pos: 0 > > > flags: 0100000 > > > mnt_id: 2 > > > userns: 4026531837 > > > > > > In [4]: print "/proc/self/ns/user -> %s" % > > > os.readlink("/proc/self/ns/user") > > > /proc/self/ns/user -> user:[4026531837] > > > > can't you just do > > > > readlink /proc/self/ns/user | sed 's/.*\[\(.*\)\]/\1/' > > We can get fdinfo for any ns file. I used /proc/self/ns/pid as an > example. > > Look at another example: > > [root@fc22-vm ~]# cat /proc/self/mountinfo | grep pid_ns_file > 115 38 0:3 pid:[4026532306] /tmp/pid_ns_file rw shared:67 - nsfs nsfs > rw > > In [4]: print open("/proc/self/fdinfo/5").read() > pos: 0 > flags: 0100000 > mnt_id: 115 > userns: 4026532305 OK, I'm missing where this is coming from specifically. There would have to be a show_fdinfo() somewhere that did this and I'm not finding it in linux-next. James