MDEV-22741: *SAN: ERROR: AddressSanitizer: use-after-poison on address in...

MDEV-22741: *SAN: ERROR: AddressSanitizer: use-after-poison on address in instrings/strmake.c:36 from change_master (on optimized builds)

Problem:
========
CHANGE MASTER TO MASTER_USER='root', MASTER_SSL=0, MASTER_SSL_CA='',
  MASTER_SSL_CERT='', MASTER_SSL_KEY='', MASTER_SSL_CRL='',
  MASTER_SSL_CRLPATH='';

CHANGE MASTER TO MASTER_USER='root', MASTER_PASSWORD='', MASTER_SSL=0;

use-after-poison is reported for lex_mi->ssl_crl

File: sql_repl.cc

if (lex_mi->ssl_crl)
  strmake_buf(mi->ssl_crl, lex_mi->ssl_crl);

Analysis:
========
At the end of CHANGE MASTER statement execution, the LEX_MASTER_INFO
parameters are reset so that the next query will have a clean state. But
'ssl_crl' and 'ssl_crl_path' members of LEX_MASTER_INFO object are not
cleared during 'LEX_MASTER_INFO::reset'. Hence when a new CHANGE MASTER
statement is executed, the stale value of lex_mi->ssl_crl is used, so ASAN
reports use-after-poison.

Fix:
===
Clear 'ssl_crl' and 'ssl_crl_path' as part of 'reset'.

mysql-test/suite/rpl/r/rpl_change_master.result

@@ -22,4 +22,8 @@ n
 connection master;
 drop table t1;
 connection slave;
+connection master;
+CHANGE MASTER TO MASTER_USER='root', MASTER_SSL=0, MASTER_SSL_CA='', MASTER_SSL_CERT='',
+MASTER_SSL_KEY='', MASTER_SSL_CRL='', MASTER_SSL_CRLPATH='';
+CHANGE MASTER TO MASTER_USER='root', MASTER_PASSWORD='', MASTER_SSL=0;
 include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_change_master.test

@@ -101,4 +101,11 @@ connection master;
 drop table t1;
 }
 
+--connection master
+# MDEV-22741: *SAN: ERROR: AddressSanitizer: use-after-poison on address in
+# instrings/strmake.c:36 from change_master (on optimized builds)
+CHANGE MASTER TO MASTER_USER='root', MASTER_SSL=0, MASTER_SSL_CA='', MASTER_SSL_CERT='',
+  MASTER_SSL_KEY='', MASTER_SSL_CRL='', MASTER_SSL_CRLPATH='';
+CHANGE MASTER TO MASTER_USER='root', MASTER_PASSWORD='', MASTER_SSL=0;
+
 --source include/rpl_end.inc

sql/sql_lex.h

@@ -280,7 +280,7 @@ struct LEX_MASTER_INFO
     }
 
     host= user= password= log_file_name= ssl_key= ssl_cert= ssl_ca=
-      ssl_capath= ssl_cipher= relay_log_name= 0;
+      ssl_capath= ssl_cipher= ssl_crl= ssl_crlpath= relay_log_name= NULL;
     pos= relay_log_pos= server_id= port= connect_retry= 0;
     heartbeat_period= 0;
     ssl= ssl_verify_server_cert= heartbeat_opt=