linux-kernel - Re: [RFC][PATCH] cgroup: Add new capability to allow a process to migrate other tasks between cgroups

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Date:   Tue, 4 Oct 2016 23:25:29 -0500
From:   "Serge E. Hallyn" <serge@...lyn.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     "Serge E. Hallyn" <serge@...lyn.com>,
        lkml <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Jonathan Corbet <corbet@....net>, cgroups@...r.kernel.org,
        Android Kernel Team <kernel-team@...roid.com>,
        Rom Lemarchand <romlem@...roid.com>,
        Colin Cross <ccross@...roid.com>,
        Dmitry Shmidt <dimitrysh@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Christian Poetzsch <christian.potzsch@...tec.com>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [RFC][PATCH] cgroup: Add new capability to allow a process to
 migrate other tasks between cgroups

On Tue, Oct 04, 2016 at 08:00:18PM -0700, John Stultz wrote:
> On Tue, Oct 4, 2016 at 5:38 PM, Serge E. Hallyn <serge@...lyn.com> wrote:
> > Quoting John Stultz (john.stultz@...aro.org):
> >> So this patch, as suggested by Tejun,  simply adds a new process
> >> capability flag (CAP_CGROUP_MIGRATE_TASK), and uses it when checking
> >
> > So realistically, what all can this mean?  Freezing tasks, changing
> > cpu/memory limits, changing network and disk throughput, forbid forking,
> > and (most importantly) forbid access to certain devices.
> >
> > I think that's all ok.  (And we still separately check for inode write
> > perms.)
> 
> Sounds good.
> 
> > If anything I'd say the GLOBAL_ROOT_UID check could be taken out since
> > otherwise a host-root task effectively cannot drop this capability.
> 
> Is this ok to leave for a separate patch?

Yeah.  And I'm not sure whether Tejun would object to that idea.

> > Acked-by: Serge Hallyn <serge@...lyn.com>
> 
> Thanks for the review!
> 
> Unless there's other feedback, I'll sit on this until the merge window
> is over and then resubmit for consideration for 4.10.
> 
> thanks
> -john