linux-kernel - Re: [bpf-next] bpf: Add CAP_NET_ADMIN for sk

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Date:   Sun, 30 Jan 2022 13:25:35 +0100
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     He Fengqing <hefengqing@...wei.com>,
        Marek Majkowski <marek@...udflare.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [bpf-next] bpf: Add CAP_NET_ADMIN for sk_lookup program type

On Sun, Jan 30, 2022 at 04:24 AM CET, Alexei Starovoitov wrote:
> On Sat, Jan 29, 2022 at 6:16 PM He Fengqing <hefengqing@...wei.com> wrote:
>>
>> SK_LOOKUP program type was introduced in commit e9ddbb7707ff
>> ("bpf: Introduce SK_LOOKUP program type with a dedicated attach point"),
>> but the commit did not add SK_LOOKUP program type in net admin prog type.
>> I think SK_LOOKUP program type should need CAP_NET_ADMIN, so add SK_LOOKUP
>> program type in net_admin_prog_type.
>
> I'm afraid it's too late to change.
>
> Jakub, Marek, wdyt?

That's definitely an oversight on my side, considering that CAP_BPF came
in 5.8, and sk_lookup program first appeared in 5.9.

Today it's possible to build a usable sk_lookup program without
CAP_NET_ADMIN if you go for REUSEPORT_SOCKARRAY map instead of
SOCKMAP/HASH.

Best I can come up is a "phase it out" approach. Put the CAP_NET_ADMIN
load-time check behind a config option, defaulting to true?, and wait
for it to become obsolete.