netdev - Re: [RFC] bpf: Emit audit messages upon successful prog load and unload

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Date:   Wed, 4 Dec 2019 15:02:51 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-audit@...hat.com,
        Andrii Nakryiko <andriin@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Steve Grubb <sgrubb@...hat.com>,
        David Miller <davem@...hat.com>,
        Eric Paris <eparis@...hat.com>, Jiri Benc <jbenc@...hat.com>
Subject: Re: [RFC] bpf: Emit audit messages upon successful prog load and
 unload

On Mon, Dec 02, 2019 at 06:00:14PM -0500, Paul Moore wrote:

SNIP

> > +
> > +static void bpf_audit_prog(const struct bpf_prog *prog, enum bpf_audit op)
> > +{
> > +       struct audit_buffer *ab;
> > +
> > +       if (audit_enabled == AUDIT_OFF)
> > +               return;
> 
> I think you would probably also want to check the results of
> audit_dummy_context() here as well, see all the various audit_XXX()
> functions in include/linux/audit.h as an example.  You'll see a
> pattern similar to the following:
> 
> static inline void audit_foo(...)
> {
>   if (unlikely(!audit_dummy_context()))
>     __audit_foo(...)
> }
> 
> > +       ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_BPF);
> > +       if (unlikely(!ab))
> > +               return;
> > +       audit_log_format(ab, "prog-id=%u op=%s",
> > +                        prog->aux->id, bpf_audit_str[op]);
> 
> Is it worth putting some checks in here to make sure that you don't
> blow past the end of the bpf_audit_str array?

forgot answer this one..  there are only 2 callers:

  bpf_audit_prog(prog, BPF_AUDIT_UNLOAD);
  bpf_audit_prog(prog, BPF_AUDIT_LOAD);

that's not going to change any time soon,
so I dont think we don't need such check

jirka