netdev - Re: [PATCH bpf-next v3 0/6] Allow updating sockmap / sockhash from BPF

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Message-ID: <CAADnVQKj5yEcRLq83B_Otp5AfY4TNWA6q9DSUGTr02kBXZmiyg@mail.gmail.com>
Date:   Fri, 21 Aug 2020 15:23:07 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     Jakub Sitnicki <jakub@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>,
        Yonghong Song <yhs@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        kernel-team <kernel-team@...udflare.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 0/6] Allow updating sockmap / sockhash from BPF

On Fri, Aug 21, 2020 at 3:30 AM Lorenz Bauer <lmb@...udflare.com> wrote:
>
> We're currently building a control plane for our BPF socket dispatch
> work. As part of that, we have a need to create a copy of an existing
> sockhash, to allow us to change the keys. I previously proposed allowing
> privileged userspace to look up sockets, which doesn't work due to
> security concerns (see [1]).
>
> In follow up discussions during BPF office hours we identified bpf_iter
> as a possible solution: instead of accessing sockets from user space
> we can iterate the source sockhash, and insert the values into a new
> map. Enabling this requires two pieces: the ability to iterate
> sockmap and sockhash, as well as being able to call map_update_elem
> from BPF.
>
> This patch set implements the latter: it's now possible to update
> sockmap from BPF context. As a next step, we can implement bpf_iter
> for sockmap.
>
> ===
>
> I've done some more fixups, and audited the safe contexts more
> thoroughly. As a result I'm removing CGROUP_SKB, SK_MSG and SK_SKB
> for now.
>
> Changes in v3:
> - Use CHECK as much as possible (Yonghong)
> - Reject ARG_PTR_TO_MAP_VALUE_OR_NULL for sockmap (Yonghong)
> - Remove CGROUP_SKB, SK_MSG, SK_SKB from safe contexts
> - Test that the verifier rejects update from unsafe context

All looks good to me.
I've applied the set.
Please follow up with a cleanup to selftests as Yonghong suggested.