From 5dc3fbf187520ff34b1b0c16c2dc27908271bcc7 Mon Sep 17 00:00:00 2001
From: "aelkin/elkin@koti.dsl.inet.fi" <>
Date: Wed, 26 Sep 2007 21:59:17 +0200
Subject: [PATCH] Bug #26000 SHOW SLAVE STATUS can crash mysqld during shutdown
 process

active_mi has been reset (shutdown) at the time of quering with
SHOW SLAVE STATUS so that
at handling of SHOW an attempt to read its members segfaults.

Fixed with checking the value of active_mi before to call show_master_info()
Merely send_ok() is invoked when active_mi does not exist.
A test can not be easiely written.

Notice, there are more analogical cases in the code which require a similar
treatment (to be reported as a bug separately).
---
 sql/sql_parse.cc | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 58f5ffc5235..075ce2c9e8c 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -2844,7 +2844,16 @@ mysql_execute_command(THD *thd)
     if (check_global_access(thd, SUPER_ACL | REPL_CLIENT_ACL))
       goto error;
     pthread_mutex_lock(&LOCK_active_mi);
-    res = show_master_info(thd,active_mi);
+    if (active_mi != NULL)
+    {
+      res = show_master_info(thd, active_mi);
+    }
+    else
+    {
+      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN, 0,
+                   "the master info structure does not exist");
+      send_ok(thd);
+    }
     pthread_mutex_unlock(&LOCK_active_mi);
     break;
   }