Update server_audit.cc

[shapled]

Fix the crash issue caused by the plugin being stopped after switching from a read lock to a write lock.

Issue #, if available:
If auditing is disabled by another thread just after the read lock is released but before acquiring the write lock, it will cause the instance to crash.

Description of changes:
Check if the logfile object has been released.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[ottok]

Hi!

Thanks for your contribution!

Seems this 2.patch the contents of them both is exactly as 1.patch:

From be9389a99e416ff25702b6d8c5262dab032ad2f2 Mon Sep 17 00:00:00 2001
From: shapled <49967374+shapled@users.noreply.github.com>
Date: Fri, 2 Jun 2023 15:25:51 +0800
Subject: [PATCH] Update server_audit.cc

Fix the crash issue caused by the plugin being stopped after switching from a read lock to a write lock.
---
 plugin/server_audit/server_audit.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/plugin/server_audit/server_audit.cc b/plugin/server_audit/server_audit.cc
index 6dd78638f37..226c3b3218e 100644
--- a/plugin/server_audit/server_audit.cc
+++ b/plugin/server_audit/server_audit.cc
@@ -1184,7 +1184,8 @@ static int write_log(const char *message, size_t len, int take_lock)
         mysql_prlock_wrlock(&lock_operations);
         allow_rotate= 1;
       }
-      if (!(is_active= (logger_write_r(logfile, allow_rotate, message, len) ==
+      if (logfile &&
+	  !(is_active= (logger_write_r(logfile, allow_rotate, message, len) ==
                         (int) len)))
       {
         ++log_write_failures;

Only difference is that this PR is targeting 5.7 while the other is for 8.0. The contents is however the same.

I will close this and do the review in #1. When #1 get's merged it will be eventually merged/cherry-picked on both branches and there is no need to duplicate submission processes.