linux-kernel - Re: [PATCH RFC v2 net-next 13/16] tracing: allow eBPF programs to be attached to events

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Date:	Wed, 23 Jul 2014 17:06:15 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	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>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 net-next 13/16] tracing: allow eBPF programs to be
 attached to events

On Wed, Jul 23, 2014 at 4:46 PM, Kees Cook <keescook@...omium.org> wrote:
>>
>> eBPF programs can call in-kernel helper functions to:
>> - lookup/update/delete elements in maps
>> - memcmp
>> - trace_printk
>> - load_pointer
>> - dump_stack
>
> Ah, this must be the pointer leaking you mentioned. :)
>
>
> Can the existing tracing mechanisms already expose kernel addresses? I
> suspect "yes". So I guess existing limitations on tracing exposure
> should already cover access control here? (I'm trying to figure out if
> a separate CONFIG is needed -- I don't think so: nothing "new" is
> exposed via eBPF, is that right?)

correct. through debugfs/tracing the whole kernel is already exposed.
Idea of eBPF for tracing is to give kernel developers and performance
engineers a tool to analyze what kernel is doing by writing programs
in C and attaching them to kprobe/tracepoint events, so it's definitely
for root only.
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