tracing: Fix use-after-free in hist_register_trigger()

This fixes a use-after-free case flagged by KASAN; make sure the test
happens before the potential free in this case.

Link: http://lkml.kernel.org/r/48fd74ab61bebd7dca9714386bb47d7c5ccd6a7b.1467247517.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_events_hist.c

@@ -1441,16 +1441,16 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 		goto out;
 	}
 
+	if (hist_data->attrs->pause)
+		data->paused = true;
+
 	if (named_data) {
 		destroy_hist_data(data->private_data);
 		data->private_data = named_data->private_data;
 		set_named_trigger_data(data, named_data);
 		data->ops = &event_hist_trigger_named_ops;
 	}
 
-	if (hist_data->attrs->pause)
-		data->paused = true;
-
 	if (data->ops->init) {
 		ret = data->ops->init(data->ops, data);
 		if (ret < 0)