netdev - RE: [PATCH v10 tip 5/9] tracing: allow BPF programs to call bpf_trace

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CB07731@AcuExch.aculab.com>
Date:	Mon, 23 Mar 2015 11:37:57 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Alexei Starovoitov' <ast@...mgrid.com>,
	Ingo Molnar <mingo@...nel.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <daniel@...earbox.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v10 tip 5/9] tracing: allow BPF programs to call
 bpf_trace_printk()

From: Alexei Starovoitov
> Debugging of BPF programs needs some form of printk from the program,
> so let programs call limited trace_printk() with %d %u %x %p modifiers only.

Should anyone be allowed to use BPF programs to determine the kernel
addresses of any items?
Looks as though it is leaking kernel addresses to userspace.
Note that the problem is with the arguments, not the format string.

	David

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