Bug#28553 mysqld crash in "purge master log before(select time from information_schema)"

forbid the use of subselect in PURGE LOGS BEFORE command


mysql-test/r/subselect.result:
  test result
mysql-test/t/subselect.test:
  test case
sql/sql_yacc.yy:
  forbid the use of subselect in PURGE LOGS BEFORE command

mysql-test/r/subselect.result

@@ -2834,6 +2834,8 @@ a
 4
 DROP TABLE t1,t2,t3;
 purge master logs before (select adddate(current_timestamp(), interval -4 day));
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'select adddate(current_timestamp(), interval -4 day))' at line 1
+purge master logs before adddate(current_timestamp(), interval -4 day);
 CREATE TABLE t1 (f1 INT);
 CREATE TABLE t2 (f2 INT);
 INSERT INTO t1 VALUES (1);

mysql-test/t/subselect.test

@@ -1815,11 +1815,12 @@ SELECT * FROM t1
 DROP TABLE t1,t2,t3;
 
 #
-# BUG #10308: purge log with subselect
+# BUG#10308: purge log with subselect
+# Bug#28553: mysqld crash in "purge master log before(select time from information_schema)"
 #
-
+--error 1064
 purge master logs before (select adddate(current_timestamp(), interval -4 day));
-
+purge master logs before adddate(current_timestamp(), interval -4 day);
 
 #
 # Bug#18503: Queries with a quantified subquery returning empty set may

sql/sql_yacc.yy

@@ -3567,7 +3567,8 @@ select_derived2:
 	  LEX *lex= Lex;
 	  lex->derived_tables= 1;
           if (lex->sql_command == (int)SQLCOM_HA_READ ||
-              lex->sql_command == (int)SQLCOM_KILL)
+              lex->sql_command == (int)SQLCOM_KILL ||
+              lex->sql_command == (int)SQLCOM_PURGE)
 	  {
 	    yyerror(ER(ER_SYNTAX_ERROR));
 	    YYABORT;
@@ -4748,6 +4749,7 @@ purge:
 	{
 	  LEX *lex=Lex;
 	  lex->type=0;
+          lex->sql_command = SQLCOM_PURGE;
 	} purge_options
 	{}
 	;
@@ -4759,7 +4761,6 @@ purge_options:
 purge_option:
         TO_SYM TEXT_STRING_sys
         {
-	   Lex->sql_command = SQLCOM_PURGE;
 	   Lex->to_log = $2.str;
         }
 	| BEFORE_SYM expr
@@ -6212,7 +6213,8 @@ subselect_start:
 	{
 	  LEX *lex=Lex;
           if (lex->sql_command == (int)SQLCOM_HA_READ ||
-              lex->sql_command == (int)SQLCOM_KILL)
+              lex->sql_command == (int)SQLCOM_KILL ||
+              lex->sql_command == (int)SQLCOM_PURGE)
 	  {
             yyerror(ER(ER_SYNTAX_ERROR));
 	    YYABORT;