Re: [PATCH v3 2/2] cgroup: allow management of subtrees by new cgroup namespaces

From: Tejun Heo
Date: Tue May 03 2016 - 11:55:21 EST

Hello, Aleksa.

On Tue, May 03, 2016 at 11:52:22AM +1000, Aleksa Sarai wrote:
> However, I agree with James that this patchset isn't ideal (it was my first
> rough attempt). I think I'll get to work on properly virtualising
> /sys/fs/cgroup, which will allow for a new cgroup namespace to modify
> subtrees (but without allowing for cgroup escape) -- by pinning what pid
> namespace the cgroup was created under. We can use the same type of
> virtualization that /proc does (except instead of selectively showing the
> dentries, we selectively show different owners of the dentries).
> Would that be acceptable?

I'm still not sold on the idea. For better or worse, the permission
model is mostly based on vfs and I don't want to deviate too much as
that's likely to become confusing pretty quickly. If a sub-hierarchy
is to be delegated, that's upto whomever is controlling cgroup
hierarchy in the sub-domain. We can expand the perm checks to
consider user namespaces but I'd like to avoid going beyond that.