MySQL Bugs: #101124: mysql batch mode execute sql failed with mysql client

Bug #101124	mysql batch mode execute sql failed with mysql client
Submitted:	12 Oct 2020 7:35	Modified:	9 Feb 2021 7:20
Reporter:	zheng shen	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Command-line Clients	Severity:	S4 (Feature request)
Version:	5.7,8.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
[root@promote ~]# mysql -uroot -pxxxx -h127.0.0.1 < 2.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1049 (42000) at line 5: Unknown database 'zhangtaodb01'

[root@promote ~]# cat 2.sql
create database zhangtaodb01;
create database zhangtaodb02;
use `zhangtaodb01`;
create table t1(id int);
DROP DATABASE IF EXISTS zhangtaodb01;
use `zhangtaodb02`;
create table t2(id int);

How to repeat:
[root@promote ~]# cat 2.sql
create database zhangtaodb01;
create database zhangtaodb02;
use `zhangtaodb01`;
create table t1(id int);
DROP DATABASE IF EXISTS zhangtaodb01;
use `zhangtaodb02`;
create table t2(id int);

mysql -uroot -pxxxx -h127.0.0.1 < /root/2.sql 
or 
mysql -uroot -pxxxx -h127.0.0.1 -e "source /root/2.sql"
will failed

[root@promote ~]# mysql -uroot -pxxxx -h127.0.0.1 < /root/2.sql
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1049 (42000) at line 5: Unknown database 'zhangtaodb01'
but
mysql -uroot -pxxxx -h127.0.0.1
> source /root/2.sql
will success

Suggested fix:
client/mysql.cc has function com_use,com_use has function get_current_db about DROP DATABASE ,but because of "use `zhangtaodb02`;" include "`". get_quote_count(line) > 0 of com_use will lead to function normalize_dbname execute.

function normalize_dbname have current_db of pointer ,current_db value is zhangtaodb01, but zhangtaodb01 of database has been droped
/* Restore the original database. */ 
if (current_db && mysql_select_db(&mysql, current_db)) return 1;

Suggested fix：
in function com_use，can I move get_current_db() before get_quote_count.

Hi Mr. shen,

Thank you for your feature request.

We have analysed it and are verifying it.

This is not a security vulnerability.

Posted by developer:
 
Fixed in 5.7.34, 8.0.24.

When the mysql client was used in batch mode, its parser could be
confused by USE followed by DROP DATABASE when the USE database name
was quoted.

Thank you, Paul ......