perf: Disallow user-space stack dumps 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'.

The user space stack dump is just another source of the this issue.

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: Vince Weaver <vincent.weaver@maine.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1393775800-13524-3-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 d5e01c3f4e69f292e3345791e7a977d29e26fabe..c894614de14d8efdbbc145141d19f9a56af9a984 100644 (file)
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -42,6 +42,13 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
                 */
                if (!p_event->attr.exclude_callchain_user)
                        return -EINVAL;
+
+               /*
+                * Same reason to disable user stack dump as for user space
+                * callchains above.
+                */
+               if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
+                       return -EINVAL;
        }
 
        /* No tracing, just counting, so no obvious leak */