netdev - Re: [PATCH bpf-next] libbpf: reject static entry-point BPF programs

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Date:   Fri, 14 May 2021 13:52:00 -0700
From:   Song Liu <song@...nel.org>
To:     Andrii Nakryiko <andrii@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] libbpf: reject static entry-point BPF programs

On Fri, May 14, 2021 at 1:33 PM Andrii Nakryiko <andrii@...nel.org> wrote:
>
> Detect use of static entry-point BPF programs (those with SEC() markings) and
> emit error message. This is similar to
> c1cccec9c636 ("libbpf: Reject static maps") but for BPF programs.
>
> Signed-off-by: Andrii Nakryiko <andrii@...nel.org>

Acked-by: Song Liu <songliubraving@...com>

> ---
>  tools/lib/bpf/libbpf.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 182bd3d3f728..e58f51b24574 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -677,6 +677,11 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
>                         return -LIBBPF_ERRNO__FORMAT;
>                 }
>
> +               if (sec_idx != obj->efile.text_shndx && GELF_ST_BIND(sym.st_info) == STB_LOCAL) {
> +                       pr_warn("sec '%s': program '%s' is static and not supported\n", sec_name, name);
> +                       return -ENOTSUP;
> +               }
> +
>                 pr_debug("sec '%s': found program '%s' at insn offset %zu (%zu bytes), code size %zu insns (%zu bytes)\n",
>                          sec_name, name, sec_off / BPF_INSN_SZ, sec_off, prog_sz / BPF_INSN_SZ, prog_sz);
>
> --
> 2.30.2
>