linux-kernel - Re: [PATCH v5] cgroup: Add new capability to allow a process to migrate other tasks between cgroups

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Message-ID: <20161213184703.GB17672@htj.duckdns.org>
Date:   Tue, 13 Dec 2016 13:47:03 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     John Stultz <john.stultz@...aro.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Li Zefan <lizefan@...wei.com>,
        Jonathan Corbet <corbet@....net>,
        "open list:CONTROL GROUP (CGROUP)" <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>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Kees Cook <keescook@...omium.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Andy Lutomirski <luto@...capital.net>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v5] cgroup: Add new capability to allow a process to
 migrate other tasks between cgroups

Hello, Casey.

On Tue, Dec 13, 2016 at 10:32:14AM -0800, Casey Schaufler wrote:
> > The trouble is that CAP_SYS_NICE or _RESOURCE (which was tried in an
> > earlier version of this patch) aren't necessarily appropriate for
> > non-android systems. See Andy's objection here:
> > https://lkml.org/lkml/2016/11/8/946
> 
> Then we need to see what those as-yet-unimplemented systems
> require and how to address them. I don't think that taking
> the "someone might want it" approach is really appropriate.

I understands that there can be reservations regarding adding a new
CAP but this isn't about someone possibly wanting it in the future.
It's more about overloading existing CAPs leading to permitting
unintended operations.  e.g. ppl who've been delegating
CAP_SYS_RESOURCES would automatically end up delegating cgroup
organization without intending so.  Using an existing cap would have
been nice but it just doesn't look like we have a good one to
overload.

Thanks.

-- 
tejun