Adding check for invalid PDCP rx PDUs

lib/src/upper/pdcp_entity.cc

@@ -168,6 +168,12 @@ void pdcp_entity::write_pdu(byte_buffer_t *pdu)
   log->info_hex(pdu->msg, pdu->N_bytes, "RX %s PDU, do_integrity = %s, do_encryption = %s",
                 rrc->get_rb_name(lcid).c_str(), (do_integrity) ? "true" : "false", (do_encryption) ? "true" : "false");
 
+  // Sanity check
+  if(pdu->N_bytes <= sn_len_bytes) {
+    pool->deallocate(pdu);
+    return;
+  }
+
   // Handle DRB messages
   if (cfg.is_data) {
     uint32_t sn;