BUG#26529369: CREATE INDEX WITH LONG COMMENT CAUSE

              UNEXPECTED ERROR

ANALYSIS:
=========
Creating many indexes with large amount of index
information causes a server exit.

FIX:
====
A appropriate error is reported when the cumulative index
information length exceeds the 2 byte range (i.e 65535).

sql/unireg.cc

 /*
-   Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -283,6 +283,25 @@ bool mysql_create_frm(THD *thd, const char *file_name,
   keybuff=(uchar*) my_malloc(key_buff_length, MYF(0));
   key_info_length= pack_keys(keybuff, keys, key_info, data_offset);
 
+  /* key_info_length is currently stored in 2 bytes */
+  if (key_info_length > 65535U)
+  {
+    char *real_table_name= (char*) table;
+    List_iterator<Create_field> it(create_fields);
+    Create_field *field;
+    while ((field=it++))
+    {
+      if (field->field && field->field->table &&
+         (real_table_name= field->field->table->s->table_name.str))
+        break;
+    }
+    my_printf_error(ER_UNKNOWN_ERROR,
+                    "Index information size for the table %s.%s exceeds the "
+                    "maximum limit (Max: 2 bytes). Please recreate indexes "
+                    "accordingly.", MYF(0), db, real_table_name);
+    goto err;
+  }
+
   /*
     Ensure that there are no forms in this newly created form file.
     Even if the form file exists, create_frm must truncate it to