cifsd: fix wrong use of rw semaphore in __session_create()

Adding list to session table should be protected by
down_write/up_write().
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifsd/mgmt/user_session.c

@@ -298,9 +298,9 @@ static struct ksmbd_session *__session_create(int protocol)
 		goto error;
 
 	if (protocol == CIFDS_SESSION_FLAG_SMB2) {
-		down_read(&sessions_table_lock);
+		down_write(&sessions_table_lock);
 		hash_add(sessions_table, &sess->hlist, sess->id);
-		up_read(&sessions_table_lock);
+		up_write(&sessions_table_lock);
 	}
 	return sess;