sctp: do not inherit ipv6_{mc|ac|fl}_list from parent

SCTP needs fixes similar to 83eaddab ("ipv6/dccp: do not inherit
ipv6_mc_list from parent"), otherwise bad things can happen.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

CVE-2017-9075

(cherry-picked from fdcee2cb)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

net/sctp/ipv6.c

@@ -662,6 +662,9 @@ static struct sock *sctp_v6_create_accept_sk(struct sock *sk,
 	newnp = inet6_sk(newsk);
 
 	memcpy(newnp, np, sizeof(struct ipv6_pinfo));
+	newnp->ipv6_mc_list = NULL;
+	newnp->ipv6_ac_list = NULL;
+	newnp->ipv6_fl_list = NULL;
 
 	rcu_read_lock();
 	opt = rcu_dereference(np->opt);