netdev - Re: [PATCH RFC net-next 08/14] bpf: add eBPF verifier

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Date:	Sat, 28 Jun 2014 18:58:50 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Alexei Starovoitov <ast@...mgrid.com>
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 08/14] bpf: add eBPF verifier

On Sat, Jun 28, 2014 at 1:25 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
> On Sat, Jun 28, 2014 at 9:01 AM, Andy Lutomirski <luto@...capital.net> wrote:
>> On Fri, Jun 27, 2014 at 5:06 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>>> Safety of eBPF programs is statically determined by the verifier, which detects:
>>
>> This is a very high-level review.  I haven't tried to read all the
>> code yet, and this is mostly questions rather than real comments.
>

> These were great questions! I hope I answered them. If not, please
> continue asking.

I have plenty more questions, but here's one right now: does anything
prevent programs from using pointers in comparisons, returning
pointers, or otherwise figuring out the value of a pointer?  If so, I
think it would be worthwhile to prevent that so that eBPF programs
can't learn kernel addresses.

--Andy
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