Bug #74794 use validate password plugin result in mysqld shutdown abnormally

Description:
when use validate_password plugin, and set some variables to 0, and set the validate_password_dictionary_file variable to one Password file，and then execute the statement:
set password = password('');
then....
server shutdown...

How to repeat:
execute sql statement as follows:

1. INSTALL PLUGIN validate_password SONAME 'validate_password.so';
2. set global validate_password_special_char_count=0;
3. set global validate_password_policy = 2;
4. set global validate_password_number_count = 0;
5. set global validate_password_mixed_case_count = 0;
6. set global validate_password_length = 0;

then test begin:

set password = password('');
then server shutdown

Suggested fix:
in function copy_if_not_alloced(), the in-parameter 'from' and 'to' will be returned respectively when different conditions, but the caller of this function(mysql_string_to_lowercase) use the return parameter to overwrite the local variable 'res', this is not the same as to the definition(String *res= new String[1];), but in code(validate_password.cc:141):mysql_string_free(lower_string_handle);
local variable 'lower_string_handle' is the return value of function mysql_string_to_lowercase(), so it can not free the different object by only one method(delete [] str) in function mysql_string_free().

Thank you for the bug report. Please try version 5.6.21:

Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.6.21-log MySQL Community Server (GPL)

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> INSTALL PLUGIN validate_password SONAME 'validate_password.dll';
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_special_char_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_policy = 2;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_number_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_mixed_case_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set password = password('');
Query OK, 0 rows affected (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sakila             |
| sgnassethealth     |
| test               |
| world              |
+--------------------+
7 rows in set (0.00 sec)

do you have set the variable validate_password_dictionary_file to one password file, and it need to include several password.
if not , please set it and test agian
thank you very much

D:\mysql-5.6.21-winx64>bin\mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.21 MySQL Community Server (GPL)

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> set global validate_password_special_char_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_policy = 2;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_number_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_mixed_case_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set password = password('');
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql>

13f3a9786    mysqld.exe!String::~String()[sql_string.h:187]
13f8e44d1    mysqld.exe!`eh vector destructor iterator'()
13f571832    mysqld.exe!mysql_string_free()[string_service.cc:55]
7feeb388ef8    validate_password.dll!validate_dictionary_check()[validate_password.cc:143]
7feeb3893ba    validate_password.dll!validate_password_policy_strength()[validate_password.cc:209]
13f47400b    mysqld.exe!check_password_policy()[sql_acl.cc:12318]
13f479ab8    mysqld.exe!change_password()[sql_acl.cc:2491]
13f46625e    mysqld.exe!set_var_password::update()[set_var.cc:799]
13f466c0f    mysqld.exe!sql_set_variables()[set_var.cc:573]
13f3f8a93    mysqld.exe!mysql_execute_command()[sql_parse.cc:3713]
13f3fadb0    mysqld.exe!mysql_parse()[sql_parse.cc:6252]
13f3fbbef    mysqld.exe!dispatch_command()[sql_parse.cc:1335]
13f3fcca7    mysqld.exe!do_command()[sql_parse.cc:1040]
13f47f0f4    mysqld.exe!do_handle_one_connection()[sql_connect.cc:982]
13f47f1aa    mysqld.exe!handle_one_connection()[sql_connect.cc:900]
13f852146    mysqld.exe!pfs_spawn_thread()[pfs.cc:1863]
13f65c46e    mysqld.exe!pthread_start()[my_winthread.c:63]
13f8eb36b    mysqld.exe!_callthreadstartex()[threadex.c:314]
13f8eb3ff    mysqld.exe!_threadstartex()[threadex.c:292]
775c59ed    kernel32.dll!BaseThreadInitThunk()
776fc541    ntdll.dll!RtlUserThreadStart()
----------------------------------------------------------------------

Thank you for the feedback. I was able to repeat with 5.6.21 but not anymore with current source:

c:\dbs>5.6\bin\mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.22 Source distribution

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> set global validate_password_special_char_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_policy = 2;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_number_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_mixed_case_count = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> set password = password('');
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like "%validate%";
+--------------------------------------+------------------+
| Variable_name                        | Value            |
+--------------------------------------+------------------+
| query_cache_wlock_invalidate         | OFF              |
| validate_password_dictionary_file    | c:\dbs\5.6\pass2 |
| validate_password_length             | 0                |
| validate_password_mixed_case_count   | 0                |
| validate_password_number_count       | 0                |
| validate_password_policy             | STRONG           |
| validate_password_special_char_count | 0                |
+--------------------------------------+------------------+
7 rows in set (0.00 sec)

So please wait for the new release.

thank you for your feedback.
do you mean this bug is existed in 5.6.21, but it is not in 5.6.22?
is it has been modified?