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  1. MariaDB Server
  2. MDEV-13084

MariaDB 10.2 crashes on corrupted SYS_TABLES.MIX_LEN field

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    Description

      MySQL 5.7 introduced a change that broke compatibility with old data files, by reading the SYS_TABLES.MIX_LEN column also for ROW_FORMAT=REDUNDANT tables, even though this column was written as uninitialized garbage in MySQL 4.1 and earlier versions.

      Because MariaDB 10.2 does not support the TABLESPACE attribute for InnoDB tables like MySQL 5.7 does, we do not need this change and can essentially revert it.

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          Bug - A problem which impairs or prevents the functions of the product. MDEV-15507 Assertion `!((flags & ((~(~0U << 1)) << 0)) >> 0) || flags2 & 16U' failed in dict_check_sys_tables on upgrade from 5.5

          • Major - Major loss of function.
          • Closed

          Activity

            marko Marko Mäkelä added a comment -

            It turns out that the logic behind the MySQL 5.7 change is sound (the garbage SYS_TABLES.MIX_LEN was written before MySQL 4.1, and before MySQL 4.1, SYS_TABLES.SPACE was always written as 0), but the error handling is incorrect. The test innodb.row_format_redundant is not really testing the corruption; it is using fault injection by DBUG_EXECUTE_IF. This would lead to a crash when dict_sys_tables_rec_read() would return an error by setting *flags2 = ULINT_UNDEFINED. The callers are only checking for flags, not flags2.

            marko Marko Mäkelä added a comment - It turns out that the logic behind the MySQL 5.7 change is sound (the garbage SYS_TABLES.MIX_LEN was written before MySQL 4.1, and before MySQL 4.1, SYS_TABLES.SPACE was always written as 0), but the error handling is incorrect. The test innodb.row_format_redundant is not really testing the corruption; it is using fault injection by DBUG_EXECUTE_IF. This would lead to a crash when dict_sys_tables_rec_read() would return an error by setting *flags2 = ULINT_UNDEFINED. The callers are only checking for flags, not flags2.

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              marko Marko Mäkelä
              marko Marko Mäkelä
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