linux-kernel - Re: [PATCH 0/2] Introduce security_create_user

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Date:   Tue, 28 Jun 2022 10:11:55 -0500
From:   Frederick Lawler <fred@...udflare.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Paul Moore <paul@...l-moore.com>,
        Christian Brauner <brauner@...nel.org>
Cc:     Casey Schaufler <casey@...aufler-ca.com>, kpsingh@...nel.org,
        revest@...omium.org, jackmanb@...omium.org, ast@...nel.org,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, jmorris@...ei.org, serge@...lyn.com,
        bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...udflare.com
Subject: Re: [PATCH 0/2] Introduce security_create_user_ns()

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@...nel.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