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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Thu, 23 Jan 2020 10:00:39 -0800
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Subject: Re: [PATCH bpf-next v3 08/10] tools/libbpf: Add support for BPF_PROG_TYPE_LSM
To:     KP Singh <kpsingh@chromium.org>
Cc:     open list <linux-kernel@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, linux-security-module@vger.kernel.org,
        Brendan Jackman <jackmanb@google.com>,
        Florent Revest <revest@google.com>,
        Thomas Garnier <thgarnie@google.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        James Morris <jmorris@namei.org>,
        Kees Cook <keescook@chromium.org>,
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        Matthew Garrett <mjg59@google.com>,
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        =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>,
        Florent Revest <revest@chromium.org>,
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        "David S. Miller" <davem@davemloft.net>,
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        Stanislav Fomichev <sdf@google.com>,
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On Thu, Jan 23, 2020 at 7:25 AM KP Singh <kpsingh@chromium.org> wrote:
>
> From: KP Singh <kpsingh@google.com>
>
> * Add functionality in libbpf to attach eBPF program to LSM hooks
> * Lookup the index of the LSM hook in security_hook_heads and pass it in
>   attr->lsm_hook_idx
>
> Signed-off-by: KP Singh <kpsingh@google.com>
> Reviewed-by: Brendan Jackman <jackmanb@google.com>
> Reviewed-by: Florent Revest <revest@google.com>
> Reviewed-by: Thomas Garnier <thgarnie@google.com>
> ---

Looks good, but see few nits below.

Acked-by: Andrii Nakryiko <andriin@fb.com>

>  tools/lib/bpf/bpf.c      |   6 ++-
>  tools/lib/bpf/bpf.h      |   1 +
>  tools/lib/bpf/libbpf.c   | 104 +++++++++++++++++++++++++++++++++++++--
>  tools/lib/bpf/libbpf.h   |   4 ++
>  tools/lib/bpf/libbpf.map |   3 ++
>  5 files changed, 114 insertions(+), 4 deletions(-)
>

[...]

> @@ -5084,6 +5099,8 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
>                 if (prog->type != BPF_PROG_TYPE_UNSPEC)
>                         continue;
>
> +
> +

why these extra lines?

>                 err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
>                                                &attach_type);
>                 if (err == -ESRCH)
> @@ -6160,6 +6177,7 @@ bool bpf_program__is_##NAME(const struct bpf_program *prog)       \
>  }                                                              \
>
>  BPF_PROG_TYPE_FNS(socket_filter, BPF_PROG_TYPE_SOCKET_FILTER);
> +BPF_PROG_TYPE_FNS(lsm, BPF_PROG_TYPE_LSM);
>  BPF_PROG_TYPE_FNS(kprobe, BPF_PROG_TYPE_KPROBE);
>  BPF_PROG_TYPE_FNS(sched_cls, BPF_PROG_TYPE_SCHED_CLS);
>  BPF_PROG_TYPE_FNS(sched_act, BPF_PROG_TYPE_SCHED_ACT);
> @@ -6226,6 +6244,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
>                                       struct bpf_program *prog);
>  static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
>                                      struct bpf_program *prog);
> +static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
> +                                  struct bpf_program *prog);
>
>  struct bpf_sec_def {
>         const char *sec;
> @@ -6272,6 +6292,9 @@ static const struct bpf_sec_def section_defs[] = {
>         SEC_DEF("freplace/", EXT,
>                 .is_attach_btf = true,
>                 .attach_fn = attach_trace),
> +       SEC_DEF("lsm/", LSM,
> +               .expected_attach_type = BPF_LSM_MAC,

curious, will there be non-MAC LSM programs? if yes, how they are
going to be different and which prefix will we use then?

> +               .attach_fn = attach_lsm),
>         BPF_PROG_SEC("xdp",                     BPF_PROG_TYPE_XDP),
>         BPF_PROG_SEC("perf_event",              BPF_PROG_TYPE_PERF_EVENT),
>         BPF_PROG_SEC("lwt_in",                  BPF_PROG_TYPE_LWT_IN),
> @@ -6533,6 +6556,44 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
>         return -EINVAL;
>  }
>
> +static __s32 find_lsm_hook_idx(struct bpf_program *prog)

nit: I'd stick to int for return result, we barely ever use __s32 in libbpf.c

[...]