Re: Potential issues (security and otherwise) with the current cgroup-bpf API

On Tue, Jan 17, 2017 at 02:03:03PM +0100, Michal Hocko wrote:

On Sun 15-01-17 20:19:01, Tejun Heo wrote:
[...]

quoted

So, what's proposed is a proper part of bpf.  In terms of
implementation, cgroup helps by hosting the pointers but that doesn't
necessarily affect the conceptual structure of it.  Given that, I
don't think it'd be a good idea to add anything to cgroup interface
for this feature.  Introspection is great to have but this should be
introspectable together with other bpf programs using the same
mechanism.  That's where it belongs.

If BPF only piggy backs on top of cgroup to iterate tasks shouldn't we
at least enforce that the cgroup has to be a leaf one and no further
children groups can be created once there is BPF program attached?

Why (again) this stupid constraint?

If you want to use cgroups for tagging (like perf does), _any_ parent
cgroup will also tag you.

So creating child cgroups, and placing tasks in it, should not be a
problem, the BPF thing should apply to all of them.