Fixed bug that MAX_USER_CONNECTIONS was not working properly in all situations (which could cause aborted connects)

thd->user_connect is now handled in thd->clenup() which will ensure that it works in all context (including slaves).
I added also some DBUG_ASSERT() to ensure that things are working correctly.


sql/sql_acl.cc:
  Reset thd->user_connect on failed check_for_max_user_connections() to ensure we don't decrement value twice.
  Removed not needed call to decrease_user_connections() as thd->cleanup() will now do it.
sql/sql_class.cc:
  Call decrease_user_connections() in thd->cleanup()
sql/sql_connect.cc:
  Ensure we don't allocate thd->user_connect twice.
  Simplify check_for_max_user_connections().
sql/sql_parse.cc:
  Ensure that thd->user_connect is handled properly in for 'change_user' command.

1 files changed, 3 insertions, 6 deletions

diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index 5eda8202f73..bea029b325b 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -8167,6 +8167,8 @@ bool acl_authenticate(THD *thd, uint connect_errors,
        max_user_connections) &&
       check_for_max_user_connections(thd, thd->user_connect))
   {
+    /* Ensure we don't decrement thd->user_connections->connections twice */
+    thd->user_connect= 0;
     status_var_increment(denied_connections);
     DBUG_RETURN(1); // The error is set in check_for_max_user_connections()
   }
@@ -8207,12 +8209,7 @@ bool acl_authenticate(THD *thd, uint connect_errors,
     if (mysql_change_db(thd, &mpvio.db, FALSE))
     {
       /* mysql_change_db() has pushed the error message. */
-      if (thd->user_connect)
-      {
-        status_var_increment(thd->status_var.access_denied_errors);
-        decrease_user_connections(thd->user_connect);
-        thd->user_connect= 0;
-      }
+      status_var_increment(thd->status_var.access_denied_errors);
       DBUG_RETURN(1);
     }
   }