ipv6: protect protocols not handling ipv4 from v4 connection/bind attempts

Some ipv6 protocols cannot handle ipv4 addresses, so we must not allow
connecting and binding to them. sendmsg logic does already check msg->name
for this but must trust already connected sockets which could be set up
for connection to ipv4 address family.

Per-socket flag ipv6only is of no use here, as it is under users control
by setsockopt.

Signed-off-by: Hannes Frederic Sowa <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ipv6.h

···
 			   char __user *optval, int __user *optlen);
 
 int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
+int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *addr,
+				 int addr_len);
 
 int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
 		    int *addr_len);

net/ipv4/ping.c

···
 		if (addr_len < sizeof(*addr))
 			return -EINVAL;
 
+		if (addr->sin6_family != AF_INET6)
+			return -EINVAL;
+
 		pr_debug("ping_check_bind_addr(sk=%p,addr=%pI6c,port=%d)\n",
 			 sk, addr->sin6_addr.s6_addr, ntohs(addr->sin6_port));
 

net/ipv6/datagram.c

···
 }
 EXPORT_SYMBOL_GPL(ip6_datagram_connect);
 
+int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *uaddr,
+				 int addr_len)
+{
+	DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, uaddr);
+	if (sin6->sin6_family != AF_INET6)
+		return -EAFNOSUPPORT;
+	return ip6_datagram_connect(sk, uaddr, addr_len);
+}
+EXPORT_SYMBOL_GPL(ip6_datagram_connect_v6_only);
+
 void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 		     __be16 port, u32 info, u8 *payload)
 {

net/ipv6/ping.c

···
 	.owner =	THIS_MODULE,
 	.init =		ping_init_sock,
 	.close =	ping_close,
-	.connect =	ip6_datagram_connect,
+	.connect =	ip6_datagram_connect_v6_only,
 	.disconnect =	udp_disconnect,
 	.setsockopt =	ipv6_setsockopt,
 	.getsockopt =	ipv6_getsockopt,

net/ipv6/raw.c

···
 
 	if (addr_len < SIN6_LEN_RFC2133)
 		return -EINVAL;
+
+	if (addr->sin6_family != AF_INET6)
+		return -EINVAL;
+
 	addr_type = ipv6_addr_type(&addr->sin6_addr);
 
 	/* Raw sockets are IPv6 only */
···
 	.owner		   = THIS_MODULE,
 	.close		   = rawv6_close,
 	.destroy	   = raw6_destroy,
-	.connect	   = ip6_datagram_connect,
+	.connect	   = ip6_datagram_connect_v6_only,
 	.disconnect	   = udp_disconnect,
 	.ioctl		   = rawv6_ioctl,
 	.init		   = rawv6_init_sk,

net/l2tp/l2tp_ip6.c

···
 	if (addr_len < sizeof(*lsa))
 		return -EINVAL;
 
+	if (usin->sin6_family != AF_INET6)
+		return -EINVAL;
+
 	addr_type = ipv6_addr_type(&usin->sin6_addr);
 	if (addr_type & IPV6_ADDR_MULTICAST)
 		return -EINVAL;