libceph: admit message frames only in CEPH_CON_S_OPEN state

Similar checks are performed for all control frames, but an early check
for message frames was missing.  process_message() is already set up to
terminate the loop in case the state changes while con->ops->dispatch()
handler is being executed.

Cc: [email protected]
Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Alex Markuze <[email protected]>
Reviewed-by: Viacheslav Dubeyko <[email protected]>

Author: idryomov

net/ceph/messenger_v2.c

@@ -2905,6 +2905,11 @@ static int __handle_control(struct ceph_connection *con, void *p)
 	if (con->v2.in_desc.fd_tag != FRAME_TAG_MESSAGE)
 		return process_control(con, p, end);
 
+	if (con->state != CEPH_CON_S_OPEN) {
+		con->error_msg = "protocol error, unexpected message";
+		return -EINVAL;
+	}
+
 	ret = process_message_header(con, p, end);
 	if (ret < 0)
 		return ret;