tracing/filters: Fix memory leak when setting a filter

Every time we set a filter, we leak memory allocated by
postfix_append_operand() and postfix_append_op().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: <stable@kernel.org> # for v2.6.31.x
LKML-Reference: <4AD3D7D9.4070400@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_events_filter.c

@@ -933,8 +933,9 @@ static void postfix_clear(struct filter_parse_state *ps)
 
 	while (!list_empty(&ps->postfix)) {
 		elt = list_first_entry(&ps->postfix, struct postfix_elt, list);
-		kfree(elt->operand);
 		list_del(&elt->list);
+		kfree(elt->operand);
+		kfree(elt);
 	}
 }