bk commit into 5.1 tree (aelkin:1.2571) BUG#26000

[Andrei Elkin]

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ChangeSet@stripped, 2007-09-12 12:13:00+03:00, aelkin@stripped +1 -0
  Bug #26000 SHOW SLAVE STATUS can crash mysqld during shutdown process
  
  active_mi has been reset at the time of quering with SHOW SLAVE STATUS.
  The handler reads members of the struct that segfaults.
  
  Fixed with ingoring show_master_info() execution if active_mi is reset.
  
  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@stripped, 2007-09-12 12:12:54+03:00, aelkin@stripped +10 -1
    Ignore reporting if master info struct has been destoyed. As this must be at shutdown merely a warning
    is sent to the client.

diff -Nrup a/sql/sql_parse.cc b/sql/sql_parse.cc
--- a/sql/sql_parse.cc	2007-08-10 23:35:20 +03:00
+++ b/sql/sql_parse.cc	2007-09-12 12:12:54 +03:00
@@ -2052,7 +2052,16 @@ 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;
   }