Multi-table update with `order by` gives wrong results

MariaDB [test]> CREATE TABLE x (id INT PRIMARY KEY AUTO_INCREMENT, filter INT, INDEX filter(filter));

Query OK, 0 rows affected (0.022 sec)

MariaDB [test]> CREATE TABLE y (id INT PRIMARY KEY AUTO_INCREMENT, x_id INT REFERENCES x(id), val FLOAT);

Query OK, 0 rows affected (0.028 sec)

MariaDB [test]> INSERT INTO x VALUES (1,1), (2,2), (3,3);

Query OK, 3 rows affected (0.009 sec)

Records: 3  Duplicates: 0  Warnings: 0

MariaDB [test]> INSERT INTO y VALUES (1,1,123), (2,2,234), (3,3,345);

Query OK, 3 rows affected (0.001 sec)

Records: 3  Duplicates: 0  Warnings: 0

MariaDB [test]> BEGIN;

Query OK, 0 rows affected (0.000 sec)

MariaDB [test]> SELECT * FROM y;

+----+------+------+

| id | x_id | val  |

+----+------+------+

|  1 |    1 |  123 |

|  2 |    2 |  234 |

|  3 |    3 |  345 |

+----+------+------+

3 rows in set (0.001 sec)

MariaDB [test]> EXPLAIN UPDATE y INNER JOIN x ON x.id = y.x_id SET y.val = y.val / 100 WHERE x.filter = 2;

+------+-------------+-------+------+----------------+--------+---------+-------+------+-------------+

| id   | select_type | table | type | possible_keys  | key    | key_len | ref   | rows | Extra       |

+------+-------------+-------+------+----------------+--------+---------+-------+------+-------------+

|    1 | SIMPLE      | x     | ref  | PRIMARY,filter | filter | 5       | const | 1    | Using index |

|    1 | SIMPLE      | y     | ALL  | x_id           | NULL   | NULL    | NULL  | 3    | Using where |

+------+-------------+-------+------+----------------+--------+---------+-------+------+-------------+

2 rows in set (0.001 sec)

MariaDB [test]> UPDATE y INNER JOIN x ON x.id = y.x_id SET y.val = y.val / 100 WHERE x.filter = 2;

Query OK, 1 row affected (0.001 sec)

Rows matched: 1  Changed: 1  Warnings: 0

MariaDB [test]> SELECT * FROM y;

+----+------+------+

| id | x_id | val  |

+----+------+------+

|  1 |    1 |  123 |

|  2 |    2 | 2.34 |

|  3 |    3 |  345 |

+----+------+------+

3 rows in set (0.001 sec)

MariaDB [test]> ROLLBACK;

Query OK, 0 rows affected (0.001 sec)

MariaDB [test]> BEGIN;

Query OK, 0 rows affected (0.000 sec)

MariaDB [test]> SELECT * FROM y;

+----+------+------+

| id | x_id | val  |

+----+------+------+

|  1 |    1 |  123 |

|  2 |    2 |  234 |

|  3 |    3 |  345 |

+----+------+------+

3 rows in set (0.001 sec)

MariaDB [test]> EXPLAIN UPDATE y INNER JOIN x ON x.id = y.x_id SET y.val = y.val / 100 WHERE x.filter = 2 ORDER BY y.val;

+------+-------------+-------+------+----------------+--------+---------+-------+------+----------------------------------------------+

| id   | select_type | table | type | possible_keys  | key    | key_len | ref   | rows | Extra                                        |

+------+-------------+-------+------+----------------+--------+---------+-------+------+----------------------------------------------+

|    1 | SIMPLE      | x     | ref  | PRIMARY,filter | filter | 5       | const | 1    | Using index; Using temporary; Using filesort |

|    1 | SIMPLE      | y     | ALL  | x_id           | NULL   | NULL    | NULL  | 3    | Using where                                  |

+------+-------------+-------+------+----------------+--------+---------+-------+------+----------------------------------------------+

2 rows in set (0.001 sec)

MariaDB [test]> UPDATE y INNER JOIN x ON x.id = y.x_id SET y.val = y.val / 100 WHERE x.filter = 2 ORDER BY y.val;

Query OK, 1 row affected (0.001 sec)

Rows matched: 1  Changed: 1  Warnings: 0

MariaDB [test]> SELECT * FROM y;

+----+------+------+

| id | x_id | val  |

+----+------+------+

|  1 |    1 |  123 |

|  2 |    2 | 3.45 |

|  3 |    3 |  345 |

+----+------+------+

3 rows in set (0.001 sec)

MariaDB [test]> ROLLBACK;

Query OK, 0 rows affected (0.000 sec)