sctp: only copy the available addr data in sctp_transport_init

'addr' passed to sctp_transport_init is not always a whole size
of union sctp_addr, like the path:

  sctp_sendmsg() ->
  sctp_sendmsg_new_asoc() ->
  sctp_assoc_add_peer() ->
  sctp_transport_new() -> sctp_transport_init()

In the next patches, we will also pass the address length of data
only to sctp_assoc_add_peer().

So sctp_transport_init() should copy the only available data from
addr to peer->ipaddr, instead of 'peer->ipaddr = *addr' which may
cause slab-out-of-bounds.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/transport.c

@@ -43,8 +43,8 @@ static struct sctp_transport *sctp_transport_init(struct net *net,
 						  gfp_t gfp)
 {
 	/* Copy in the address.  */
-	peer->ipaddr = *addr;
 	peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
+	memcpy(&peer->ipaddr, addr, peer->af_specific->sockaddr_len);
 	memset(&peer->saddr, 0, sizeof(union sctp_addr));
 
 	peer->sack_generation = 0;