Assertion fail / Memory leak in `mariadb-binlog --force-read`

Code Analysis

Log_event::read_log_event(IO_CACHE*, ...) has an assertion saying that error cases should not generate an event:

  if (unlikely(error))

  {

    DBUG_ASSERT(!res);

But a checksum error in Log_event::read_log_event(const uchar *buf, ...) outputs both an error message and, under --force-read, an Unknown_log_event substitute.

MDEV-35643's explicit refute of TRANSACTION_PAYLOAD_EVENT and PARTIAL_UPDATE_ROWS_EVENT events also have the same problematic code pattern.
(This means a perfectly valid MySQL binlog can trigger this bug.)

On non-debug (release) builds that don't include assertions, the snippet immediately after this assertion ends the function without cleaning up the unexpected Unknown_log_event, which is a memory leak.

    if (force_opt)

      DBUG_RETURN(new Unknown_log_event());

MTR Reproduction

--source include/have_debug.inc

--source include/have_binlog_format_mixed.inc # format-agnostic

RESET MASTER;

FLUSH BINARY LOGS;

--let $MYSQLD_DATADIR= `SELECT @@datadir`

--echo #MYSQL_BINLOG --verify-binlog-checksum --force-read --debug=d,simulate_checksum_test_failure #MYSQLD_DATADIR/master-bin.000001 2>&1

--exec $MYSQL_BINLOG --verify-binlog-checksum --force-read --debug=d,simulate_checksum_test_failure $MYSQLD_DATADIR/master-bin.000001 2>&1

Fix Recommendation

Since --force-read is defined as "output invalid events as 'Unknown event's rather than error", the conditions above should output an Unknown_log_event but not an error.