netdev - Re: [PATCH v2 bpf-next 1/3] capability: introduce CAP_BPF and CAP

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Date:   Thu, 29 Aug 2019 15:36:42 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Alexei Starovoitov <ast@...nel.org>, luto@...capital.net
Cc:     davem@...emloft.net, peterz@...radead.org, rostedt@...dmis.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...com,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next 1/3] capability: introduce CAP_BPF and
 CAP_TRACING

Le 29/08/2019 à 07:12, Alexei Starovoitov a écrit :
[snip]
> CAP_BPF and CAP_NET_ADMIN together allow the following:
> - Attach to cgroup-bpf hooks and query
> - skb, xdp, flow_dissector test_run command
> 
> CAP_NET_ADMIN allows:
> - Attach networking bpf programs to xdp, tc, lwt, flow dissector
I'm not sure to understand the difference between these last two points.
But, with the current kernel, CAP_NET_ADMIN is not enough to attach bpf prog
with tc and it's still not enough after your patch.
The following command is rejected:
$ tc filter add dev eth0 ingress matchall action bpf obj ./tc_test_kern.o sec test

Prog section 'test' rejected: Operation not permitted (1)!
 - Type:         4
 - Instructions: 22 (0 over limit)
 - License:      GPL

Verifier analysis:

Error fetching program/map!
bad action parsing
parse_action: bad value (5:bpf)!
Illegal "action"
$


Like Andy, I'm also wondering about the backward compatibility. With my current
docker, I'm able to play with tc bpf with CAP_SYS_ADMIN. But if I update my
kernel with your patches, CAP_SYS_ADMIN doesn't allow anymore that and CAP_BPF
is not implemented in my current docker, thus I cannot give the correct
capabilities. In other words, an old docker cannot run on a new kernel.

Regards,
Nicolas