linux-kernel - Re: [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks

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Message-ID: <20200324015217.GA28487@chromium.org>
Date:   Tue, 24 Mar 2020 02:52:21 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks

On 23-Mär 18:13, Casey Schaufler wrote:
> On 3/23/2020 9:44 AM, KP Singh wrote:
> > From: KP Singh <kpsingh@...gle.com>
> >
> > The bpf_lsm_ nops are initialized into the LSM framework like any other
> > LSM.  Some LSM hooks do not have 0 as their default return value. The
> > __weak symbol for these hooks is overridden by a corresponding
> > definition in security/bpf/hooks.c
> >
> > +	return 0;

[...]

> > +}
> > +
> > +DEFINE_LSM(bpf) = {
> > +	.name = "bpf",
> > +	.init = bpf_lsm_init,
> 
> Have you given up on the "BPF must be last" requirement?

Yes, we dropped it for as the BPF programs require CAP_SYS_ADMIN
anwyays so the position ~shouldn't~ matter. (based on some of the
discussions we had on the BPF_MODIFY_RETURN patches).

However, This can be added later (in a separate patch) if really
deemed necessary.

- KP

> 
> > +};