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From:   Paul Moore <paul@paul-moore.com>
Date:   Tue, 28 Jun 2022 11:13:05 -0400
Message-ID: <CAHC9VhQq4smKbQdLJzb_yGQ2VfPWJ6wK8onUh_Np0uU7zAa3rQ@mail.gmail.com>
Subject: Re: [PATCH 0/2] Introduce security_create_user_ns()
To:     Frederick Lawler <fred@cloudflare.com>
Cc:     Daniel Borkmann <daniel@iogearbox.net>,
        Christian Brauner <brauner@kernel.org>,
        Casey Schaufler <casey@schaufler-ca.com>, kpsingh@kernel.org,
        revest@chromium.org, jackmanb@chromium.org, ast@kernel.org,
        andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
        john.fastabend@gmail.com, jmorris@namei.org, serge@hallyn.com,
        bpf@vger.kernel.org, linux-security-module@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@cloudflare.com
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On Tue, Jun 28, 2022 at 11:11 AM Frederick Lawler <fred@cloudflare.com> wrote:
> On 6/27/22 5:15 PM, Daniel Borkmann wrote:
> > On 6/27/22 11:56 PM, Paul Moore wrote:
> >> On Mon, Jun 27, 2022 at 8:11 AM Christian Brauner <brauner@kernel.org>
> >> wrote:
> >>> On Thu, Jun 23, 2022 at 11:21:37PM -0400, Paul Moore wrote:
> >>
> >> ...
> >>
> >>>> This is one of the reasons why I usually like to see at least one LSM
> >>>> implementation to go along with every new/modified hook.  The
> >>>> implementation forces you to think about what information is necessary
> >>>> to perform a basic access control decision; sometimes it isn't always
> >>>> obvious until you have to write the access control :)
> >>>
> >>> I spoke to Frederick at length during LSS and as I've been given to
> >>> understand there's a eBPF program that would immediately use this new
> >>> hook. Now I don't want to get into the whole "Is the eBPF LSM hook
> >>> infrastructure an LSM" but I think we can let this count as a legitimate
> >>> first user of this hook/code.
> >>
> >> Yes, for the most part I don't really worry about the "is a BPF LSM a
> >> LSM?" question, it's generally not important for most discussions.
> >> However, there is an issue unique to the BPF LSMs which I think is
> >> relevant here: there is no hook implementation code living under
> >> security/.  While I talked about a hook implementation being helpful
> >> to verify the hook prototype, it is also helpful in providing an
> >> in-tree example for other LSMs; unfortunately we don't get that same
> >> example value when the initial hook implementation is a BPF LSM.
> >
> > I would argue that such a patch series must come together with a BPF
> > selftest which then i) contains an in-tree usage example, ii) adds BPF
> > CI test coverage. Shipping with a BPF selftest at least would be the
> > usual expectation.
>
> Sounds good. I'll add both a eBPF selftest and SELinux implementation
> for v2.

Thanks Daniel!

-- 
paul-moore.com