MySQL Bugs: #119766: Rows unexpectedly added in performance

Bug #119766	Rows unexpectedly added in performance_schema for failed connections
Submitted:	23 Jan 19:18
Reporter:	Aaron Newberg	Email Updates:
Status:	Open	Impact on me:	None
Category:	MySQL Server: Performance Schema	Severity:	S2 (Serious)
Version:	8.0.44	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Starting in 8.0.44, failed connection attempts add a row to performance_schema.accounts, performance_schema.users, and others.

Rows should only be added when authentication succeeds.

For example, in performance_schema.accounts:
When authentication fails, we expect the table with NULL for USER and HOST to be updated.
See documentation:
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-accounts-table.html#:~:text=for...

However, starting in 8.0.44, a new row is created for failed connection attempts.

If many failed connection attempts are issued from unique users (that may or may not exist), performance_schema can become bloated and use more memory than it should.

How to repeat:
1. Enable performance_schema and restart
2. Try to connect to MySQL as a user that does not exist (FYI anonymous user ''@'%' must not be present)
3. 'select * performance_schema.accounts' and observe the row created for the user from step 2

Suggested fix:
Revert https://github.com/mysql/mysql-server/commit/a7ad97839cfb2302fe5985fd5964bb4301d62bbf#diff...

The change in sql_authentication.cc runs the PSI instrumentation code for all connection attempts.