Re: [PATCH 4/4] cgroup/bpf: Honor cgroup NS in cgroup_iter for ancestors

[Michal Koutný]

On Fri, Aug 26, 2022 at 10:41:37AM -0700, Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:
> I understand that currently cgroup_iter is the only user of this, but
> for future use cases, is it safe to assume that cgrp will always be
> inside ns? Would it be safer to do something like:

I preferred the simpler root_cgrp comparison to avoid pointer
arithmetics in cgroup_is_descendant. But I also made the assumption of
cgrp in ns.

Thanks, I'll likely adjust cgroup_path_ns to make it more robust for
an external cgrp.


I'd like to clarify, if a process A in a broad cgroup ns sets up a BPF
cgroup iterator, exposes it via bpffs and than a process B in a narrowed
cgroup ns (which excludes the origin cgroup) wants to traverse the
iterator, should it fail straight ahead (regardless of iter order)?
The alternative would be to allow self-dereference but prohibit any
iterator moves (regardless of order).


Thanks,
Michal

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