From: "Serge E. Hallyn" <serge@hallyn.com>
To: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
criu@openvz.org, Linux API <linux-api@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Containers <containers@lists.linux-foundation.org>,
Andy Lutomirski <luto@amacapital.net>,
Tycho Andersen <tycho.andersen@canonical.com>
Subject: Re: Introspecting userns relationships to other namespaces?
Date: Thu, 7 Jul 2016 08:36:31 -0500 [thread overview]
Message-ID: <20160707133631.GA2994@mail.hallyn.com> (raw)
In-Reply-To: <CAKgNAkhtQNg0mVv6ei_JigNz3njo_G3opE+rzd4OtKpa2hQe9g@mail.gmail.com>
Quoting Michael Kerrisk (man-pages) (mtk.manpages@gmail.com):
> Hi Serge,
>
> On 6 July 2016 at 16:13, Serge E. Hallyn <serge@hallyn.com> wrote:
> > On Wed, Jul 06, 2016 at 10:41:48AM +0200, Michael Kerrisk (man-pages) wrote:
> >> [Rats! Doing now what I should have down to start with. Looping some
> >> lists and CRIU and other possibly relevant people into this
> >> conversation]
> >>
> >> Hi Eric,
> >>
> >> On 5 July 2016 at 23:47, Eric W. Biederman <ebiederm@xmission.com> wrote:
> >> > "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes:
> >> >
> >> >> Hi Eric,
> >> >>
> >> >> I have a question. Is there any way currently to discover which
> >> >> user namespace a particular nonuser namespace is governed by?
> >> >> Maybe I am missing something, but there does not seem to be a
> >> >> way to do this. Also, can one discover which userns is the
> >> >> parent of a given userns? Again, I can't see a way to do this.
> >> >>
> >> >> The point here is introspecting so that a process might determine
> >> >> what its capabilities are when operating on some resource governed
> >> >> by a (nonuser) namespace.
> >> >
> >> > To the best of my knowledge that there is not an interface to get that
> >> > information. It would be good to have such an interface for no other
> >> > reason than the CRIU folks are going to need it at some point. I am a
> >> > bit surprised they have not complained yet.
> >
> > I don't think they need it. They do in fact have what they need. Assume
> > you have tasks T1, T2, T1_1 and T2_1; T1 and T2 are in init_user_ns; T1
> > spawned T1_1 in a new userns; T2 spawned T2_1 which setns()d to T1_1's ns.
> > There's some {handwave} uid mapping, does not matter.
> >
> > At restart, it doesn't matter which task originally created the new userns.
> > criu knows T1_1 and T2_1 are in the same userns; it creates the userns, sets
> > up the mapping, and T1_1 and T2_1 setns() to it.
>
> I'm missing something here. How does the parental relationships
> between the user namespaces get reconstructed? Those relationships
> will govern what capabilities a process will have in various user
> namespaces.
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.
next prev parent reply other threads:[~2016-07-07 13:37 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <c2a26220-69f2-f2f5-491a-e43abd9a6f92@gmail.com>
[not found] ` <87r3b7pxja.fsf@x220.int.ebiederm.org>
2016-07-06 8:41 ` Introspecting userns relationships to other namespaces? Michael Kerrisk (man-pages)
2016-07-06 14:13 ` Serge E. Hallyn
2016-07-06 15:46 ` Eric W. Biederman
2016-07-08 1:57 ` [CRIU] " Andrew Vagin
2016-07-08 7:44 ` Eric W. Biederman
2016-07-08 14:35 ` James Bottomley
2016-07-08 20:38 ` Andrew Vagin
2016-07-08 20:50 ` W. Trevor King
2016-07-08 22:19 ` James Bottomley
2016-07-08 22:19 ` James Bottomley
2016-07-08 23:52 ` Eric W. Biederman
2016-07-09 0:15 ` James Bottomley
2016-07-09 3:05 ` Eric W. Biederman
2016-07-09 7:26 ` Andrew Vagin
2016-07-09 10:31 ` James Bottomley
2016-07-09 10:32 ` James Bottomley
2016-07-09 18:15 ` Eric W. Biederman
2016-07-09 18:29 ` Eric W. Biederman
2016-07-13 0:08 ` Andrew Vagin
2016-07-13 3:59 ` W. Trevor King
2016-07-07 8:15 ` Michael Kerrisk (man-pages)
2016-07-07 13:36 ` Serge E. Hallyn [this message]
2016-07-07 15:01 ` James Bottomley
2016-07-07 18:21 ` Michael Kerrisk (man-pages)
2016-07-07 18:24 ` Serge E. Hallyn
2016-07-07 19:17 ` James Bottomley
2016-07-08 2:16 ` [CRIU] " Andrew Vagin
2016-07-08 3:00 ` Andrew Vagin
2016-07-08 3:26 ` James Bottomley
2016-07-08 5:26 ` W. Trevor King
2016-07-08 6:16 ` W. Trevor King
2016-07-08 6:54 ` Andrew Vagin
2016-07-08 7:18 ` W. Trevor King
2016-07-08 5:41 ` [CRIU] " Andrei Vagin
2016-07-08 5:47 ` Andrei Vagin
2016-07-08 6:07 ` James Bottomley
2016-07-08 11:17 ` Michael Kerrisk (man-pages)
2016-07-08 3:20 ` James Bottomley
2016-07-08 6:09 ` Andrew Vagin
2016-07-08 11:11 ` Michael Kerrisk (man-pages)
2016-07-09 3:15 ` W. Trevor King
2016-07-09 3:13 ` Eric W. Biederman
2016-07-10 5:36 ` [CRIU] " Andrew Vagin
2016-07-10 20:29 ` Eric W. Biederman
2016-07-10 21:06 ` James Bottomley
2016-07-11 20:55 ` Andrew Vagin
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