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

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Date:   Mon, 26 Feb 2018 20:57:46 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     Sargun Dhillon <sargun@...gun.me>
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 07:49:48PM -0800, Sargun Dhillon wrote:
> 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.

Oh, right. So can't we just drop this, and the existing code will
DTRT, i.e. give you -EMEDIUMTYPE because the new filters aren't
supported, until they are?

Tycho