dr_05: add boundary checking

src/descriptors/dr_05.c

@@ -74,6 +74,9 @@ dvbpsi_registration_dr_t * dvbpsi_DecodeRegistrationDr(
                                    | ((uint32_t)(p_descriptor->p_data[2]) << 8)
                                    | (uint32_t)(p_descriptor->p_data[3]);
   p_decoded->i_additional_length = p_descriptor->i_length - 4;
+  if (p_decoded->i_additional_length > 251)
+      p_decoded->i_additional_length = 251;
+
   if(p_decoded->i_additional_length)
     memcpy(p_decoded->i_additional_info,
            p_descriptor->p_data + 4,
@@ -91,6 +94,9 @@ dvbpsi_registration_dr_t * dvbpsi_DecodeRegistrationDr(
 dvbpsi_descriptor_t * dvbpsi_GenRegistrationDr(dvbpsi_registration_dr_t *p_decoded,
                                                bool b_duplicate)
 {
+    if (p_decoded->i_additional_length > 251)
+        p_decoded->i_additional_length = 251;
+
     /* Create the descriptor */
     dvbpsi_descriptor_t * p_descriptor =
             dvbpsi_NewDescriptor(0x05, p_decoded->i_additional_length + 4, NULL);