Bug#27980823: HEAP OVERFLOW VULNERABILITIES IN MYSQL CLIENT LIBRARY

(cherry picked from commit b5b986b2cbd9a7848dc3f48e5c42b6d4e1e5fb22)

sql-common/client.c

@@ -1505,7 +1505,8 @@ unpack_fields(MYSQL *mysql, MYSQL_DATA *data,MEM_ROOT *alloc,uint fields,
     {
       uchar *pos;
       /* fields count may be wrong */
-      DBUG_ASSERT((uint) (field - result) < fields);
+      if (field < result || (uint) (field - result) >= fields)
+        DBUG_RETURN(NULL);
       cli_fetch_lengths(&lengths[0], row->data, default_value ? 8 : 7);
       field->catalog=   strmake_root(alloc,(char*) row->data[0], lengths[0]);
       field->db=        strmake_root(alloc,(char*) row->data[1], lengths[1]);
@@ -1612,6 +1613,7 @@ MYSQL_DATA *cli_read_rows(MYSQL *mysql,MYSQL_FIELD *mysql_fields,
 
   if ((pkt_len= cli_safe_read(mysql)) == packet_error)
     DBUG_RETURN(0);
+  if (pkt_len == 0) DBUG_RETURN(0);
   if (!(result=(MYSQL_DATA*) my_malloc(sizeof(MYSQL_DATA),
 				       MYF(MY_WME | MY_ZEROFILL))))
   {