Re: [syzbot] [fs?] WARNING: bad unlock balance in seq_read_iter

[Edward Adam Davis]

#syz test

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 4cb275316e51..dad032912e1e 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1600,11 +1600,12 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 	struct set_event_iter *iter;
 	loff_t l;
 
+	mutex_lock(&event_mutex);
+
 	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
-	if (!iter)
+	if (!iter) {
 		return NULL;
-
-	mutex_lock(&event_mutex);
+	}
 
 	iter->type = SET_EVENT_FILE;
 	iter->file = list_entry(&tr->events, struct trace_event_file, list);