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 20:00:18 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     "Serge E. Hallyn" <serge@...lyn.com>
Cc:     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 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?

> 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