tracing: fix leak in event_format_read()

Impact: fix memory leak

If event_format_read() exits early due to nonzero ppos, the
previous kmalloc doesn't get freed - might as well do the
check before the kmalloc and avoid the problem.
Signed-off-by: NTom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237270859.8033.141.camel@charm-linux>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/trace_events.c

@@ -378,15 +378,15 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
 	char *buf;
 	int r;
 
+	if (*ppos)
+		return 0;
+
 	s = kmalloc(sizeof(*s), GFP_KERNEL);
 	if (!s)
 		return -ENOMEM;
 
 	trace_seq_init(s);
 
-	if (*ppos)
-		return 0;
-
 	/* If any of the first writes fail, so will the show_format. */
 
 	trace_seq_printf(s, "name: %s\n", call->name);