Bug #110502 Incorrect output of FIELD function

• Submitted: 25 Mar 2023 22:03
• Modified: 28 Mar 2023 6:11
• Reporter: Zuming Jiang
• Status: Not a Bug
• Category: MySQL Server: Optimizer
• Severity: S2 (Serious)
• Version: 8.0, 5.7
• OS: Any
• CPU Architecture: Any

[25 Mar 2023 22:03] Zuming Jiang

Description:
My fuzzer found a bug in the MySQL server. This bug made the FIELD() function return incorrect results.

How to repeat:
** Test case**

select FIELD('o', null, '');
select FIELD('o', null + 1, '');

** Expected Behavior **

Two SELECT should output the same results {0}, because null + 1 is null.

** Actual Behavior **

select FIELD('o', null, ''); --- output {0}
select FIELD('o', null + 1, ''); --- output {2}

One outputs {0} and another one outputs {2}.

[26 Mar 2023 7:39] MySQL Verification Team

Hello Zuming Jiang,

Thank you for the report and test case.

regards,
Umesh

[27 Mar 2023 13:06] Tor Didriksen

Posted by developer:
 
select FIELD('o', null, ');
the function operates on strings, 'o' and ' are not equal

select FIELD('o', null + 1, ');
the function operates on doubles, and both 'o' and ' convert to 0.0

https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_field