sctp: discard ABORT chunk with zero verification tag in COOKIE-WAIT state

In current implementation if ABORT chunk is received with T flag is set
and zero verification tag in COOKIE-WAIT state, the ABORT chunk will be
always accepted. This is because in COOKIE-WAIT state, the endpoint does
not know the peer's verification tag, and it's zero in the endpoint.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

include/net/sctp/sm.h

@@ -437,7 +437,7 @@ sctp_vtag_verify_either(const struct sctp_chunk *chunk,
 	 */
         if ((!sctp_test_T_bit(chunk) &&
              (ntohl(chunk->sctp_hdr->vtag) == asoc->c.my_vtag)) ||
-	    (sctp_test_T_bit(chunk) &&
+	    (sctp_test_T_bit(chunk) && asoc->c.peer_vtag &&
 	     (ntohl(chunk->sctp_hdr->vtag) == asoc->c.peer_vtag))) {
                 return 1;
 	}