netdev - Re: [PATCH bpf-next 1/3] bpf: preserve command of the process that loaded the program

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Date:   Fri, 11 Oct 2019 17:10:58 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 1/3] bpf: preserve command of the process that
 loaded the program

On Fri, Oct 11, 2019 at 9:21 AM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Even though we have the pointer to user_struct and can recover
> uid of the user who has created the program, it usually contains
> 0 (root) which is not very informative. Let's store the comm of the
> calling process and export it via bpf_prog_info. This should help
> answer the question "which process loaded this particular program".
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  include/linux/bpf.h      | 1 +
>  include/uapi/linux/bpf.h | 2 ++
>  kernel/bpf/syscall.c     | 4 ++++
>  3 files changed, 7 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 5b9d22338606..b03ea396afe5 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -421,6 +421,7 @@ struct bpf_prog_aux {
>                 struct work_struct work;
>                 struct rcu_head rcu;
>         };
> +       char created_by_comm[BPF_CREATED_COMM_LEN];
>  };
>
>  struct bpf_array {
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index a65c3b0c6935..4e883ecbba1e 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -326,6 +326,7 @@ enum bpf_attach_type {
>  #define BPF_F_NUMA_NODE                (1U << 2)
>
>  #define BPF_OBJ_NAME_LEN 16U
> +#define BPF_CREATED_COMM_LEN   16U

Nack.
16 bytes is going to be useless.
We found it the hard way with prog_name.
If you want to embed additional debug information
please use BTF for that.