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>

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index e854f420e033eb65a2bca233bb8df2e42778faf7..d5e01c3f4e69f292e3345791e7a977d29e26fabe 100644 (file)
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -31,9 +31,18 @@ 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))
-               return -EPERM;
+       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))