From: Andy Lutomirski <luto@amacapital.net>
To: "Eric W.Biederman" <ebiederm@xmission.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
Aditya Kali <adityakali@google.com>,
Linux API <linux-api@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Serge Hallyn <serge.hallyn@ubuntu.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Tejun Heo <tj@kernel.org>,
cgroups@vger.kernel.org, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCHv1 7/8] cgroup: cgroup namespace setns support
Date: Mon, 20 Oct 2014 17:20:44 -0700 [thread overview]
Message-ID: <CALCETrXhGnBM_xx=Auz3WRQXkqhGGTWuZN=PU+A9HZ7Ek27FLA@mail.gmail.com> (raw)
In-Reply-To: <44072106-c0f3-46b8-b2b5-9b1cbd1b7d88@email.android.com>
On Sun, Oct 19, 2014 at 9:55 PM, Eric W.Biederman <ebiederm@xmission.com> wrote:
>
>
> On October 19, 2014 1:26:29 PM CDT, Andy Lutomirski <luto@amacapital.net> wrote:
>>On Sat, Oct 18, 2014 at 10:23 PM, Eric W. Biederman
>><ebiederm@xmission.com> wrote:
>>> "Serge E. Hallyn" <serge@hallyn.com> writes:
>>>
>>>> Quoting Aditya Kali (adityakali@google.com):
>>>>> On Thu, Oct 16, 2014 at 2:12 PM, Serge E. Hallyn <serge@hallyn.com>
>>wrote:
>>>>> > Quoting Aditya Kali (adityakali@google.com):
>>>>> >> setns on a cgroup namespace is allowed only if
>>>>> >> * task has CAP_SYS_ADMIN in its current user-namespace and
>>>>> >> over the user-namespace associated with target cgroupns.
>>>>> >> * task's current cgroup is descendent of the target
>>cgroupns-root
>>>>> >> cgroup.
>>>>> >
>>>>> > What is the point of this?
>>>>> >
>>>>> > If I'm a user logged into
>>>>> > /lxc/c1/user.slice/user-1000.slice/session-c12.scope and I start
>>>>> > a container which is in
>>>>> > /lxc/c1/user.slice/user-1000.slice/session-c12.scope/x1
>>>>> > then I will want to be able to enter the container's cgroup.
>>>>> > The container's cgroup root is under my own (satisfying the
>>>>> > below condition0 but my cgroup is not a descendent of the
>>>>> > container's cgroup.
>>>>> >
>>>>> This condition is there because we don't want to do implicit cgroup
>>>>> changes when a process attaches to another cgroupns. cgroupns tries
>>to
>>>>> preserve the invariant that at any point, your current cgroup is
>>>>> always under the cgroupns-root of your cgroup namespace. But in
>>your
>>>>> example, if we allow a process in "session-c12.scope" container to
>>>>> attach to cgroupns root'ed at "session-c12.scope/x1" container
>>>>> (without implicitly moving its cgroup), then this invariant won't
>>>>> hold.
>>>>
>>>> Oh, I see. Guess that should be workable. Thanks.
>>>
>>> Which has me looking at what the rules are for moving through
>>> the cgroup hierarchy.
>>>
>>> As long as we have write access to cgroup.procs and are allowed
>>> to open the file for write, we can move any of our own tasks
>>> into the cgroup. So the cgroup namespace rules don't seem
>>> to be a problem.
>>>
>>> Andy can you please take a look at the permission checks in
>>> __cgroup_procs_write.
>>
>>The actual requirements for calling that function haven't changed,
>>right? IOW, what does this have to do with cgroupns?
>
> Excluding user namespaces the requirements have not changed.
>
> The immediate correlation is that to enter a cgroupns you must first put your process in one of it's cgroups.
>
> So I was examining what it would take to enter the cgroup of cgroupns.
>
>> Is the idea
>>that you want a privileged user wrt a cgroupns's userns to be able to
>>use this? If so:
>>
>>Yes, that current_cred() thing is bogus. (Actually, this is probably
>>exploitable right now if any cgroup.procs inode anywhere on the system
>>lets non-root write.) (Can we have some kernel debugging option that
>>makes any use of current_cred() in write(2) warn?)
>>
>>We really need a weaker version of may_ptrace for this kind of stuff.
>>Maybe the existing may_ptrace stuff is okay, actually. But this is
>>completely missing group checks, cap checks, capabilities wrt the
>>userns, etc.
>>
>>Also, I think that, if this version of the patchset allows non-init
>>userns to unshare cgroupns, then the issue of what permission is
>>needed to lock the cgroup hierarchy like that needs to be addressed,
>>because unshare(CLONE_NEWUSER|CLONE_NEWCGROUP) will effectively pin
>>the calling task with no permission required. Bolting on a fix later
>>will be a mess.
>
> I imagine the pinning would be like the userns.
>
> Ah but there is a potentially serious issue with the pinning.
> With pinning we can make it impossible for root to move us to a different cgroup.
>
> I am not certain how serious that is but it bears thinking about.
> If we don't implement pinning we should be able to implent everything with just filesystem mount options, and no new namespace required.
>
> Sigh.
>
> I am too tired tonight to see the end game in this.
Possible solution:
Ditch the pinning. That is, if you're outside a cgroupns (or you have
a non-ns-confined cgroupfs mounted), then you can move a task in a
cgroupns outside of its root cgroup. If you do this, then the task
thinks its cgroup is something like "../foo" or "../../foo".
While we're at it, consider making setns for a cgroupns *not* change
the caller's cgroup. Is there any reason it really needs to?
Thoughts?
--Andy
next prev parent reply other threads:[~2014-10-21 0:21 UTC|newest]
Thread overview: 157+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <adityakali-cgroupns>
2014-07-17 19:52 ` [PATCH 0/5] RFC: CGroup Namespaces Aditya Kali
2014-07-17 19:52 ` [PATCH 1/5] kernfs: Add API to get generate relative kernfs path Aditya Kali
2014-07-24 15:10 ` Serge Hallyn
2014-07-17 19:52 ` [PATCH 2/5] sched: new clone flag CLONE_NEWCGROUP for cgroup namespace Aditya Kali
2014-07-24 17:01 ` Serge Hallyn
2014-07-31 19:48 ` Aditya Kali
2014-08-04 23:12 ` Serge Hallyn
2014-07-17 19:52 ` [PATCH 3/5] cgroup: add function to get task's cgroup on default hierarchy Aditya Kali
2014-07-24 16:59 ` Serge Hallyn
2014-07-17 19:52 ` [PATCH 4/5] cgroup: export cgroup_get() and cgroup_put() Aditya Kali
2014-07-24 17:03 ` Serge Hallyn
2014-07-17 19:52 ` [PATCH 5/5] cgroup: introduce cgroup namespaces Aditya Kali
2014-07-17 19:57 ` Andy Lutomirski
2014-07-17 20:55 ` Aditya Kali
2014-07-18 16:51 ` Andy Lutomirski
2014-07-18 18:51 ` Aditya Kali
2014-07-18 18:57 ` Andy Lutomirski
2014-07-21 22:11 ` Aditya Kali
2014-07-21 22:16 ` Andy Lutomirski
2014-07-23 19:52 ` Aditya Kali
2014-07-18 16:00 ` [PATCH 0/5] RFC: CGroup Namespaces Serge Hallyn
2014-07-24 16:10 ` Serge Hallyn
2014-07-24 16:36 ` Serge Hallyn
2014-07-25 19:29 ` Aditya Kali
2014-07-25 20:27 ` Andy Lutomirski
2014-07-29 4:51 ` Serge E. Hallyn
2014-07-29 15:08 ` Andy Lutomirski
2014-07-29 16:06 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 0/8] " Aditya Kali
2014-10-13 21:23 ` [PATCHv1 1/8] kernfs: Add API to generate relative kernfs path Aditya Kali
2014-10-16 16:07 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 2/8] sched: new clone flag CLONE_NEWCGROUP for cgroup namespace Aditya Kali
2014-10-16 16:08 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 3/8] cgroup: add function to get task's cgroup on default hierarchy Aditya Kali
2014-10-16 16:13 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 4/8] cgroup: export cgroup_get() and cgroup_put() Aditya Kali
2014-10-16 16:14 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 5/8] cgroup: introduce cgroup namespaces Aditya Kali
2014-10-16 16:37 ` Serge E. Hallyn
2014-10-24 1:03 ` Aditya Kali
2014-10-25 3:16 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 6/8] cgroup: restrict cgroup operations within task's cgroupns Aditya Kali
2014-10-17 9:28 ` Serge E. Hallyn
2014-10-22 19:06 ` Aditya Kali
2014-10-19 4:57 ` Eric W. Biederman
2014-10-13 21:23 ` [PATCHv1 7/8] cgroup: cgroup namespace setns support Aditya Kali
2014-10-16 21:12 ` Serge E. Hallyn
2014-10-16 21:17 ` Andy Lutomirski
2014-10-16 21:22 ` Aditya Kali
2014-10-16 21:47 ` Serge E. Hallyn
2014-10-19 5:23 ` Eric W. Biederman
2014-10-19 18:26 ` Andy Lutomirski
2014-10-20 4:55 ` Eric W.Biederman
2014-10-21 0:20 ` Andy Lutomirski [this message]
2014-10-21 4:49 ` Eric W. Biederman
2014-10-21 5:03 ` Andy Lutomirski
2014-10-21 5:42 ` Eric W. Biederman
2014-10-21 5:49 ` Andy Lutomirski
2014-10-21 18:49 ` Aditya Kali
2014-10-21 19:02 ` Andy Lutomirski
2014-10-21 22:33 ` Aditya Kali
2014-10-21 22:42 ` Andy Lutomirski
2014-10-22 0:46 ` Aditya Kali
2014-10-22 0:58 ` Andy Lutomirski
2014-10-22 18:37 ` Aditya Kali
2014-10-22 18:50 ` Andy Lutomirski
2014-10-22 19:42 ` Tejun Heo
2014-10-17 9:52 ` Serge E. Hallyn
2014-10-13 21:23 ` [PATCHv1 8/8] cgroup: mount cgroupns-root when inside non-init cgroupns Aditya Kali
2014-10-17 12:19 ` Serge E. Hallyn
2014-10-14 22:42 ` [PATCHv1 0/8] CGroup Namespaces Andy Lutomirski
2014-10-14 23:33 ` Aditya Kali
2014-10-19 4:54 ` Eric W. Biederman
2015-07-22 18:10 ` Vincent Batts
2014-10-31 19:18 ` [PATCHv2 0/7] " Aditya Kali
2014-10-31 19:18 ` [PATCHv2 1/7] kernfs: Add API to generate relative kernfs path Aditya Kali
2014-10-31 19:18 ` [PATCHv2 2/7] sched: new clone flag CLONE_NEWCGROUP for cgroup namespace Aditya Kali
2014-10-31 19:18 ` [PATCHv2 3/7] cgroup: add function to get task's cgroup on default hierarchy Aditya Kali
2014-10-31 19:18 ` [PATCHv2 4/7] cgroup: export cgroup_get() and cgroup_put() Aditya Kali
2014-10-31 19:18 ` [PATCHv2 5/7] cgroup: introduce cgroup namespaces Aditya Kali
2014-11-01 0:02 ` Andy Lutomirski
2014-11-01 0:58 ` Eric W. Biederman
2014-11-03 23:42 ` Aditya Kali
2014-11-03 23:40 ` Aditya Kali
2014-11-04 1:56 ` Aditya Kali
2014-10-31 19:19 ` [PATCHv2 6/7] cgroup: cgroup namespace setns support Aditya Kali
2014-10-31 19:19 ` [PATCHv2 7/7] cgroup: mount cgroupns-root when inside non-init cgroupns Aditya Kali
2014-11-01 0:07 ` Andy Lutomirski
2014-11-01 2:59 ` Eric W. Biederman
2014-11-01 3:29 ` Andy Lutomirski
2014-11-03 23:12 ` Aditya Kali
2014-11-03 23:15 ` Andy Lutomirski
2014-11-03 23:23 ` Aditya Kali
2014-11-03 23:48 ` Andy Lutomirski
2014-11-04 0:12 ` Aditya Kali
2014-11-04 0:17 ` Andy Lutomirski
2014-11-04 0:49 ` Aditya Kali
2014-11-04 13:57 ` Tejun Heo
2014-11-06 17:28 ` Aditya Kali
2014-11-01 1:09 ` Eric W. Biederman
2014-11-03 22:46 ` Aditya Kali
[not found] ` <CAGr1F2Hd_PS_AscBGMXdZC9qkHGRUp-MeQvJksDOQkRBB3RGoA@mail.gmail.com>
2014-11-03 22:56 ` Andy Lutomirski
2014-11-04 13:46 ` Tejun Heo
2014-11-04 15:00 ` Andy Lutomirski
2014-11-04 15:50 ` Serge E. Hallyn
2014-11-12 17:48 ` Aditya Kali
2014-11-04 1:59 ` Aditya Kali
2014-11-04 13:10 ` [PATCHv2 0/7] CGroup Namespaces Vivek Goyal
2014-11-06 17:33 ` Aditya Kali
2014-11-26 22:58 ` Richard Weinberger
2014-12-02 19:14 ` Aditya Kali
2014-12-05 1:55 ` [PATCHv3 0/8] " Aditya Kali
2014-12-05 1:55 ` [PATCHv3 1/8] kernfs: Add API to generate relative kernfs path Aditya Kali
2014-12-05 1:55 ` [PATCHv3 2/8] sched: new clone flag CLONE_NEWCGROUP for cgroup namespace Aditya Kali
2014-12-05 1:55 ` [PATCHv3 3/8] cgroup: add function to get task's cgroup on default hierarchy Aditya Kali
2014-12-05 1:55 ` [PATCHv3 4/8] cgroup: export cgroup_get() and cgroup_put() Aditya Kali
2014-12-05 1:55 ` [PATCHv3 5/8] cgroup: introduce cgroup namespaces Aditya Kali
2014-12-12 8:54 ` Zefan Li
2014-12-05 1:55 ` [PATCHv3 6/8] cgroup: cgroup namespace setns support Aditya Kali
2014-12-05 1:55 ` [PATCHv3 7/8] cgroup: mount cgroupns-root when inside non-init cgroupns Aditya Kali
2014-12-12 8:55 ` Zefan Li
2014-12-05 1:55 ` [PATCHv3 8/8] cgroup: Add documentation for cgroup namespaces Aditya Kali
2014-12-12 8:54 ` Zefan Li
2015-01-05 22:54 ` Aditya Kali
2014-12-14 23:05 ` Richard Weinberger
2015-01-05 22:48 ` Aditya Kali
2015-01-05 22:52 ` Richard Weinberger
2015-01-05 23:53 ` Eric W. Biederman
2015-01-06 0:07 ` Richard Weinberger
2015-01-06 0:10 ` Aditya Kali
2015-01-06 0:17 ` Richard Weinberger
2015-01-06 23:20 ` Aditya Kali
2015-01-06 23:39 ` Richard Weinberger
2015-01-07 9:28 ` Richard Weinberger
2015-01-07 14:45 ` Eric W. Biederman
2015-01-07 19:30 ` Serge E. Hallyn
2015-01-07 22:14 ` Eric W. Biederman
2015-01-07 22:45 ` Tejun Heo
2015-01-07 23:02 ` Eric W. Biederman
2015-01-07 23:06 ` Tejun Heo
2015-01-07 23:09 ` Eric W. Biederman
2015-01-07 23:16 ` Tejun Heo
2015-01-07 23:27 ` Eric W. Biederman
2015-01-07 23:35 ` Tejun Heo
2015-02-11 3:46 ` Serge E. Hallyn
2015-02-11 4:09 ` Tejun Heo
2015-02-11 4:29 ` Serge E. Hallyn
2015-02-11 5:02 ` Eric W. Biederman
2015-02-11 5:17 ` Tejun Heo
2015-02-11 6:29 ` Eric W. Biederman
2015-02-11 14:36 ` Tejun Heo
2015-02-11 16:00 ` Serge E. Hallyn
2015-02-11 16:03 ` Tejun Heo
2015-02-11 16:18 ` Serge E. Hallyn
2015-02-11 5:10 ` Tejun Heo
2015-01-07 18:57 ` Aditya Kali
2014-12-05 3:20 ` [PATCHv3 0/8] CGroup Namespaces Aditya Kali
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CALCETrXhGnBM_xx=Auz3WRQXkqhGGTWuZN=PU+A9HZ7Ek27FLA@mail.gmail.com' \
--to=luto@amacapital.net \
--cc=adityakali@google.com \
--cc=cgroups@vger.kernel.org \
--cc=containers@lists.linux-foundation.org \
--cc=ebiederm@xmission.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=serge.hallyn@ubuntu.com \
--cc=serge@hallyn.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).