linux-kernel - Re: [PATCH 4/4] cgroup/bpf: Honor cgroup NS in cgroup

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Date:   Mon, 29 Aug 2022 11:02:36 -0700
From:   Hao Luo <haoluo@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Yosry Ahmed <yosryahmed@...gle.com>,
        Michal Koutný <mkoutny@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Aditya Kali <adityakali@...gle.com>,
        Serge Hallyn <serge.hallyn@...onical.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Yonghong Song <yhs@...com>,
        Muneendra Kumar <muneendra.kumar@...adcom.com>
Subject: Re: [PATCH 4/4] cgroup/bpf: Honor cgroup NS in cgroup_iter for ancestors

On Mon, Aug 29, 2022 at 10:49 AM Tejun Heo <tj@...nel.org> wrote:
>
> On Mon, Aug 29, 2022 at 10:30:45AM -0700, Yosry Ahmed wrote:
> > > 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).
> > >
> >
> > imo it should fail straight ahead, but maybe others (Tejun? Hao?) have
> > other opinions here.
>
> Yeah, I'd prefer it to fail right away as that's simple and gives us the
> most choices for the future.
>

Thanks Michal for fixing the cgroup iter use case! I agree that
failing straight ahead is better. I don't envision a use case that
wants the alternative.

> Thanks.
>
> --
> tejun