When a socket sock object is in DCCP_LISTEN state and connect() system call is being called with AF_UNSPEC, the dccp_disconnect() puts sock state into DCCP_CLOSED, and forgets to free dccps_hc_rx_ccid/dccps_hc_tx_ccid and assigns NULL to them, then when we call connect() again with AF_INET6 sockaddr family, the sock object gets cloned via dccp_create_openreq_child() and returns a new sock object, which holds references of dccps_hc_rx_ccid and dccps_hc_tx_ccid of the old sock object, and this leads to both the old and new sock objects can use the same memory.