tracing: Fix minor bugs for __unregister_ftrace_function_probe

Fix the condition of strcmp for "*".
Also fix NULL pointer dereference when glob is NULL.
Signed-off-by: NAtsushi Tsuji <a-tsuji@bk.jp.nec.com>
LKML-Reference: <4AAF6726.5090905@bk.jp.nec.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -2062,9 +2062,9 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 	int i, len = 0;
 	char *search;
 
-	if (glob && (strcmp(glob, "*") || !strlen(glob)))
+	if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
 		glob = NULL;
-	else {
+	else if (glob) {
 		int not;
 
 		type = ftrace_setup_glob(glob, strlen(glob), &search, &not);