netdev - RE: [PATCH RFC net-next 07/14] bpf: expand BPF syscall with program load/unload

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Date:	Mon, 30 Jun 2014 10:06:23 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Alexei Starovoitov' <ast@...mgrid.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	"Jiri Olsa" <jolsa@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	"Network Development" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH RFC net-next 07/14] bpf: expand BPF syscall with program
 load/unload

From: Alexei Starovoitov
> On Fri, Jun 27, 2014 at 5:19 PM, Andy Lutomirski <luto@...capital.net> wrote:
> > On Fri, Jun 27, 2014 at 5:05 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
> >> eBPF programs are safe run-to-completion functions with load/unload
> >> methods from userspace similar to kernel modules.
> >>
> >> User space API:
> >>
> >> - load eBPF program
> >>   prog_id = bpf_prog_load(int prog_id, bpf_prog_type, struct nlattr *prog, int len)
> >>
> >>   where 'prog' is a sequence of sections (currently TEXT and LICENSE)
> >>   TEXT - array of eBPF instructions
> >>   LICENSE - GPL compatible
> >> +
> >> +       err = -EINVAL;
> >> +       /* look for mandatory license string */
> >> +       if (!tb[BPF_PROG_LICENSE])
> >> +               goto free_attr;
> >> +
> >> +       /* eBPF programs must be GPL compatible */
> >> +       if (!license_is_gpl_compatible(nla_data(tb[BPF_PROG_LICENSE])))
> >> +               goto free_attr;
> >
> > Seriously?  My mind boggles.
> 
> Yes. Quite a bit of logic can fit into one eBPF program. I don't think it's wise
> to leave this door open for abuse. This check makes it clear that if you
> write a program in C, the source code must be available.

That seems utterly extreme.
Loadable kernel modules don't have to be GPL.

I can imagine that some people might not want to load code for which
they don't have the source - but in that case they probably want to
compile it themselves anyway.

I don't want to have to put a gpl licence on random pieces of test
code I might happen to write for my own use.

	David