In the Linux kernel, the following vulnerability has been resolved:
mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable().
mptcp_active_enable() is called from subflow_finish_connect(),
which is icsk->icsk_af_ops->sk_rx_dst_set() and it's not always
under RCU.
Using sk_dst_get(sk)->dev could trigger UAF.
Let's use __sk_dst_get() and dst_dev_rcu().
