sctp: asconf's process should verify address parameter is in the beginning

in sctp_process_asconf(), we get address parameter from the beginning of
the addip params. but we never check if it's really there. if the addr
param is not there, it still can pass sctp_verify_asconf(), then to be
handled by sctp_process_asconf(), it will not be safe.

so add a code in sctp_verify_asconf() to check the address parameter is in
the beginning, or return false to send abort.

note that this can also detect multiple address parameters, and reject it.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_make_chunk.c

@@ -3132,11 +3132,18 @@ bool sctp_verify_asconf(const struct sctp_association *asoc,
 		case SCTP_PARAM_IPV4_ADDRESS:
 			if (length != sizeof(sctp_ipv4addr_param_t))
 				return false;
+			/* ensure there is only one addr param and it's in the
+			 * beginning of addip_hdr params, or we reject it.
+			 */
+			if (param.v != addip->addip_hdr.params)
+				return false;
 			addr_param_seen = true;
 			break;
 		case SCTP_PARAM_IPV6_ADDRESS:
 			if (length != sizeof(sctp_ipv6addr_param_t))
 				return false;
+			if (param.v != addip->addip_hdr.params)
+				return false;
 			addr_param_seen = true;
 			break;
 		case SCTP_PARAM_ADD_IP: