netdev - Re: [net-next v3 1/2] bpf, seccomp: Add eBPF filter capabilities

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Date:   Mon, 26 Feb 2018 19:49:48 -0800
From:   Sargun Dhillon <sargun@...gun.me>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     netdev <netdev@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Will Drewry <wad@...omium.org>,
        Kees Cook <keescook@...omium.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [net-next v3 1/2] bpf, seccomp: Add eBPF filter capabilities

On Mon, Feb 26, 2018 at 4:54 PM, Tycho Andersen <tycho@...ho.ws> wrote:
> On Mon, Feb 26, 2018 at 07:27:05AM +0000, Sargun Dhillon wrote:
>> +config SECCOMP_FILTER_EXTENDED
>> +     bool "Extended BPF seccomp filters"
>> +     depends on SECCOMP_FILTER && BPF_SYSCALL
>> +     depends on !CHECKPOINT_RESTORE
>
> Why not just give -EINVAL or something in case one of these is
> requested, instead of making them incompatible at compile time?
>
> Tycho
There's already code to return -EMEDIUMTYPE if it's a non-classic, or
non-saved filter. Under the normal case, with CHECKPOINT_RESTORE
enabled, you should never be able to get that. I think it makes sense
to preserve this behaviour.

My rough plan is to introduce a mechanism to dump filters like you can
cBPF filters. If you look at my v1, there was a patch that did this.
Once this gets in, I can prepare that patch, and we can lift this
restriction.