Commit cfa77bc4 authored Mar 02, 2014 by Jiri Olsa Committed by Ingo Molnar Mar 11, 2014

perf: Disallow user-space callchains for function trace events

Recent issues with user space callchains processing within
page fault handler tracing showed as Peter said 'there's
just too much fail surface'.

Related list discussions:

  http://marc.info/?t=139302086500001&r=1&w=2
  http://marc.info/?t=139301437300003&r=1&w=2



Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1393775800-13524-2-git-send-email-jolsa@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent ef11dadb

kernel/trace/trace_event_perf.c

+12 −3

Original line number	Diff line number	Diff line
		@@ -31,10 +31,19 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
		}

		/* The ftrace function trace is allowed only for root. */
		if (ftrace_event_is_function(tp_event) &&
		perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
		if (ftrace_event_is_function(tp_event)) {
		if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
		return -EPERM;

		/*
		* We don't allow user space callchains for function trace
		* event, due to issues with page faults while tracing page
		* fault handler and its overall trickiness nature.
		*/
		if (!p_event->attr.exclude_callchain_user)
		return -EINVAL;
		}

		/* No tracing, just counting, so no obvious leak */
		if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
		return 0;