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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Thu, 11 Feb 2021 18:28:54 -0800
Message-ID: <CAADnVQ+e7P9SeDFUQ58tX8PAEf+bymWBXXboO+Qv8AO2DS5YWQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next v7 2/5] bpf: Expose bpf_get_socket_cookie to
 tracing programs
To:     Florent Revest <revest@chromium.org>
Cc:     bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        KP Singh <kpsingh@chromium.org>,
        Florent Revest <revest@google.com>,
        Brendan Jackman <jackmanb@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>,
        KP Singh <kpsingh@kernel.org>
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On Wed, Feb 10, 2021 at 3:14 AM Florent Revest <revest@chromium.org> wrote:
>
> +BPF_CALL_1(bpf_get_socket_ptr_cookie, struct sock *, sk)
> +{
> +       return sk ? sock_gen_cookie(sk) : 0;
> +}
> +
> +const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto = {
> +       .func           = bpf_get_socket_ptr_cookie,
> +       .gpl_only       = false,
> +       .ret_type       = RET_INTEGER,
> +       .arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
> +};

As Daniel pointed out there is an sk_destruct issue here, but I don't
think it's fair
to penalize this set and future similar patches. They don't make things worse.
The issue has been there for some time due to sk_storage in tracing and
other helpers. We need to come up with a holistic approach to solve it.
I suspect allow/deny lists will certainly make it better, but won't
really address it,
and will be fragile over long term.
I think tracing would need to be integrated with bpf_lsm and start relying
on security_*_free callbacks to cover this last 1%.
I think that would be a great topic for the next bpf office hours on Feb 25.