MDEV-30453 Setting innodb_buffer_pool_filename to an empty string attempts to delete the data directory on shutdown

Let us make innodb_buffer_pool_filename a read-only variable
so that a malicious user cannot cause an important file to be
deleted on InnoDB shutdown. An attempt to delete a directory
will fail because it is not a regular file, but what if the
variable pointed to (say) ibdata1, ib_logfile0 or some *.ibd file?

It does not seem to make much sense for this parameter to be
configurable in the first place, but we will not change that in order
to avoid breaking compatibility.

mysql-test/suite/innodb/r/innodb_buffer_pool_dump_pct.result

@@ -2,13 +2,11 @@ CREATE TABLE tab5 (col1 int auto_increment primary key,
 col2 VARCHAR(25), col3 varchar(25)) ENGINE=InnoDB;
 CREATE INDEX idx1 ON tab5(col2(10));
 CREATE INDEX idx2 ON tab5(col3(10));
-SET GLOBAL innodb_buffer_pool_filename=ib_buffer_pool100;
 SET GLOBAL innodb_buffer_pool_dump_pct=100;
 SELECT variable_value INTO @IBPDS
 FROM information_schema.global_status
 WHERE variable_name = 'INNODB_BUFFER_POOL_DUMP_STATUS';
 SET GLOBAL innodb_buffer_pool_dump_now=ON;
-SET GLOBAL innodb_buffer_pool_filename=ib_buffer_pool1;
 SET GLOBAL innodb_buffer_pool_dump_pct=1;
 SELECT @@global.innodb_buffer_pool_dump_pct;
 @@global.innodb_buffer_pool_dump_pct
@@ -18,5 +16,4 @@ FROM information_schema.global_status
 WHERE variable_name = 'INNODB_BUFFER_POOL_DUMP_STATUS';
 SET GLOBAL innodb_buffer_pool_dump_now=ON;
 SET GLOBAL innodb_buffer_pool_dump_pct=DEFAULT;
-SET GLOBAL innodb_buffer_pool_filename=DEFAULT;
 DROP TABLE tab5;

mysql-test/suite/innodb/r/innodb_sys_var_valgrind.result

@@ -25,27 +25,6 @@ select @@innodb_ft_server_stopword_table;
 @@innodb_ft_server_stopword_table
 NULL
 drop table user_stopword_1, user_stopword_2;
-select @@innodb_buffer_pool_filename;
-@@innodb_buffer_pool_filename
-ib_buffer_pool
-set @blah='hello';
-set global innodb_buffer_pool_filename = @blah;
-select @@innodb_buffer_pool_filename;
-@@innodb_buffer_pool_filename
-hello
-set global innodb_buffer_pool_filename="bye";
-select @@innodb_buffer_pool_filename;
-@@innodb_buffer_pool_filename
-bye
-set global innodb_buffer_pool_filename=NULL;
-ERROR 42000: Variable 'innodb_buffer_pool_filename' can't be set to the value of 'NULL'
-select @@innodb_buffer_pool_filename;
-@@innodb_buffer_pool_filename
-bye
-set global innodb_buffer_pool_filename=default;
-select @@innodb_buffer_pool_filename;
-@@innodb_buffer_pool_filename
-ib_buffer_pool
 CREATE TABLE t1 ( id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
 opening_line TEXT(500), author VARCHAR(200), title VARCHAR(200), FULLTEXT idx
 (opening_line)) ENGINE=InnoDB;

mysql-test/suite/innodb/t/innodb_buffer_pool_dump_pct.test

@@ -15,7 +15,6 @@ col2 VARCHAR(25), col3 varchar(25)) ENGINE=InnoDB;
 CREATE INDEX idx1 ON tab5(col2(10));
 CREATE INDEX idx2 ON tab5(col3(10));
 
-SET GLOBAL innodb_buffer_pool_filename=ib_buffer_pool100;
 SET GLOBAL innodb_buffer_pool_dump_pct=100;
 
 #***********************************************************
@@ -58,8 +57,7 @@ AND variable_value != @IBPDS
 AND variable_value like 'Buffer pool(s) dump completed at%';
 --source include/wait_condition.inc
 
---file_exists $MYSQLD_DATADIR/ib_buffer_pool100
-SET GLOBAL innodb_buffer_pool_filename=ib_buffer_pool1;
+--move_file $MYSQLD_DATADIR/ib_buffer_pool $MYSQLD_DATADIR/ib_buffer_pool100
 SET GLOBAL innodb_buffer_pool_dump_pct=1;
 SELECT @@global.innodb_buffer_pool_dump_pct;
 
@@ -83,17 +81,15 @@ AND variable_value != @IBPDS
 AND variable_value like 'Buffer pool(s) dump completed at%';
 --source include/wait_condition.inc
 
---file_exists $MYSQLD_DATADIR/ib_buffer_pool1
+--file_exists $MYSQLD_DATADIR/ib_buffer_pool
 
 perl;
-my $size1 = -s "$ENV{MYSQLD_DATADIR}/ib_buffer_pool1";
+my $size1 = -s "$ENV{MYSQLD_DATADIR}/ib_buffer_pool";
 my $size100 = -s "$ENV{MYSQLD_DATADIR}/ib_buffer_pool100";
 die "$size100<=$size1\n" unless $size100 > $size1;
 EOF
 
 SET GLOBAL innodb_buffer_pool_dump_pct=DEFAULT;
-SET GLOBAL innodb_buffer_pool_filename=DEFAULT;
 
 --remove_file $MYSQLD_DATADIR/ib_buffer_pool100
---remove_file $MYSQLD_DATADIR/ib_buffer_pool1
 DROP TABLE tab5;

mysql-test/suite/innodb/t/innodb_sys_var_valgrind.test

@@ -25,24 +25,6 @@ select @@innodb_ft_server_stopword_table;
 
 drop table user_stopword_1, user_stopword_2;
 
-#Test innodb_buffer_pool_filename (global variable)
-
-select @@innodb_buffer_pool_filename;
-
-set @blah='hello';
-set global innodb_buffer_pool_filename = @blah;
-select @@innodb_buffer_pool_filename;
-
-set global innodb_buffer_pool_filename="bye";
-select @@innodb_buffer_pool_filename;
-
---error ER_WRONG_VALUE_FOR_VAR
-set global innodb_buffer_pool_filename=NULL;
-select @@innodb_buffer_pool_filename;
-
-set global innodb_buffer_pool_filename=default;
-select @@innodb_buffer_pool_filename;
-
 #Test innodb_ft_aux_table (global variable)
 CREATE TABLE t1 ( id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
 opening_line TEXT(500), author VARCHAR(200), title VARCHAR(200), FULLTEXT idx

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -221,7 +221,7 @@ NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
 ENUM_VALUE_LIST	NULL
-READ_ONLY	NO
+READ_ONLY	YES
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	INNODB_BUFFER_POOL_INSTANCES
 SESSION_VALUE	NULL

storage/innobase/handler/ha_innodb.cc

@@ -18020,44 +18020,6 @@ exit:
 	return;
 }
 
-/** Validate SET GLOBAL innodb_buffer_pool_filename.
-On Windows, file names with colon (:) are not allowed.
-@param thd   connection
-@param save  &srv_buf_dump_filename
-@param value new value to be validated
-@return	0 for valid name */
-static int innodb_srv_buf_dump_filename_validate(THD *thd, st_mysql_sys_var*,
-						 void *save,
-						 st_mysql_value *value)
-{
-  char buff[OS_FILE_MAX_PATH];
-  int len= sizeof buff;
-
-  if (const char *buf_name= value->val_str(value, buff, &len))
-  {
-#ifdef _WIN32
-    if (!is_filename_allowed(buf_name, len, FALSE))
-    {
-      push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
-			  ER_WRONG_ARGUMENTS,
-			  "InnoDB: innodb_buffer_pool_filename "
-			  "cannot have colon (:) in the file name.");
-      return 1;
-    }
-#endif /* _WIN32 */
-    if (buf_name == buff)
-    {
-      ut_ad(static_cast<size_t>(len) < sizeof buff);
-      buf_name= thd_strmake(thd, buf_name, len);
-    }
-
-    *static_cast<const char**>(save)= buf_name;
-    return 0;
-  }
-
-  return 1;
-}
-
 #ifdef UNIV_DEBUG
 static char* srv_buffer_pool_evict;
 
@@ -19363,9 +19325,9 @@ static MYSQL_SYSVAR_ULONG(buffer_pool_instances, srv_buf_pool_instances,
   NULL, NULL, srv_buf_pool_instances_default, 0, MAX_BUFFER_POOLS, 0);
 
 static MYSQL_SYSVAR_STR(buffer_pool_filename, srv_buf_dump_filename,
-  PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_MEMALLOC,
+  PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "Filename to/from which to dump/load the InnoDB buffer pool",
-  innodb_srv_buf_dump_filename_validate, NULL, SRV_BUF_DUMP_FILENAME_DEFAULT);
+  NULL, NULL, SRV_BUF_DUMP_FILENAME_DEFAULT);
 
 static MYSQL_SYSVAR_BOOL(buffer_pool_dump_now, innodb_buffer_pool_dump_now,
   PLUGIN_VAR_RQCMDARG,