[tip:perf/core] perf: Disallow user-space callchains for function trace events

[tip-bot for Jiri Olsa]

Commit-ID:  cfa77bc4af2c75c0781ee76cde2dd104c6c8e2b7
Gitweb:     http://git.kernel.org/tip/cfa77bc4af2c75c0781ee76cde2dd104c6c8e2b7
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Sun, 2 Mar 2014 16:56:38 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 11 Mar 2014 11:57:57 +0100

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@xxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1393775800-13524-2-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/trace/trace_event_perf.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index e854f42..d5e01c3 100644
--- 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))
--
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