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

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Date:   Mon, 27 Jun 2022 17:56:14 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Frederick Lawler <fred@...udflare.com>,
        Casey Schaufler <casey@...aufler-ca.com>, kpsingh@...nel.org,
        revest@...omium.org, jackmanb@...omium.org, ast@...nel.org,
        daniel@...earbox.net, 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 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.

-- 
paul-moore.com