linux-kernel - Re: [PATCH bpf-next v1 04/13] bpf: lsm: Allow btf

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Message-ID: <20191230192245.GA18663@chromium.org>
Date:   Mon, 30 Dec 2019 20:22:45 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, linux-security-module@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...omium.org>,
        Michael Halcrow <mhalcrow@...gle.com>,
        Paul Turner <pjt@...gle.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Mickaël Salaün <mic@...ikod.net>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Andrey Ignatov <rdna@...com>, Joe Stringer <joe@...d.net.nz>
Subject: Re: [PATCH bpf-next v1 04/13] bpf: lsm: Allow btf_id based
 attachment for LSM hooks

On 23-Dez 15:54, Andrii Nakryiko wrote:
> On Fri, Dec 20, 2019 at 7:42 AM KP Singh <kpsingh@...omium.org> wrote:
> >
> > From: KP Singh <kpsingh@...gle.com>
> >
> > Refactor and re-use most of the logic for BPF_PROG_TYPE_TRACING with a few
> > changes.
> >
> > - The LSM hook BTF types are prefixed with "lsm_btf_"

Got rid of this for v2 as we are using trampoline. Will keep this in
mind if we ever need to generate type information. Thanks!

> 
> btf_trace_ and btf_struct_ops all have btf_ first, let's keep this consistent.
> 
> > - These types do not need the first (void *) pointer argument. The verifier
> >   only looks for this argument if prod->aux->attach_btf_trace is set.
> >
> > Signed-off-by: KP Singh <kpsingh@...gle.com>
> > ---
> >  kernel/bpf/syscall.c  |  1 +
> >  kernel/bpf/verifier.c | 83 ++++++++++++++++++++++++++++++++++++++++---
> >  2 files changed, 80 insertions(+), 4 deletions(-)
> >
> 
> [...]
> 
> > +
> > +       t = btf_type_by_id(btf_vmlinux, btf_id);
> > +       if (!t) {
> > +               verbose(env, "attach_btf_id %u is invalid\n", btf_id);
> > +               return -EINVAL;
> > +       }
> > +
> > +       tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > +       if (!tname) {
> 
> it can be empty, so better: !tname || !tname[0]

Will fix the usages in v2. 

- KP
> 
> > +               verbose(env, "attach_btf_id %u doesn't have a name\n", btf_id);
> > +               return -EINVAL;
> > +       }
> > +
> 
> [...]