linux-kernel - Re: [PATCH bpf 1/2] flow_dissector: reject invalid attach

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Date:   Fri, 12 Jun 2020 15:35:49 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        kernel-team <kernel-team@...udflare.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf 1/2] flow_dissector: reject invalid attach_flags

On Fri, Jun 12, 2020 at 9:02 AM Lorenz Bauer <lmb@...udflare.com> wrote:
>
> Using BPF_PROG_ATTACH on a flow dissector program supports neither flags
> nor target_fd but accepts any value. Return EINVAL if either are non-zero.
>
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
> Fixes: b27f7bb590ba ("flow_dissector: Move out netns_bpf prog callbacks")
> ---
>  kernel/bpf/net_namespace.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c
> index 78cf061f8179..56133e78ae4f 100644
> --- a/kernel/bpf/net_namespace.c
> +++ b/kernel/bpf/net_namespace.c
> @@ -192,6 +192,9 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
>         struct net *net;
>         int ret;
>
> +       if (attr->attach_flags || attr->target_fd)
> +               return -EINVAL;
> +

In theory it makes sense, but how did you test it?
test_progs -t flow
fails 5 tests.