tracing/filters: disallow integer values for string filters and vice versa

Impact: fix filter use boundary condition / crash

Make sure filters for string fields don't use integer values and vice
versa.  Getting it wrong can crash the system or produce bogus
results.
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237878882.8339.61.camel@charm-linux>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_events_filter.c

@@ -237,9 +237,14 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
 	pred->offset = field->offset;
 
 	if (is_string_field(field->type)) {
+		if (!pred->str_val)
+			return -EINVAL;
 		pred->fn = filter_pred_string;
 		pred->str_len = field->size;
 		return __filter_add_pred(call, pred);
+	} else {
+		if (pred->str_val)
+			return -EINVAL;
 	}
 
 	switch (field->size) {