Fix counter leak in nonsuper_connections (#1069)

Summary:
If a non-super user connects to mysqld with an invalid database name,
nonsuper_connections is incremented, but never decremented.

Squash with D13987618

8.0 porting notes:
Since nonsuper_connections is already decremented by calling
release_user_connection(), changes to the code are not needed. Test is
ported though to make sure the leak won't appear again.

Reference Patch: 3cc5162fdc2

Pull Request resolved: #1069

Reviewed By: yizhang82

Differential Revision: D19129736

Pulled By: hermanlee

fbshipit-source-id: 64a9117

mysql-test/r/max_nonsuper_connections.result

@@ -51,6 +51,27 @@ disconnect con4;
 disconnect con3;
 disconnect con2;
 disconnect con1;
+Verifying nonsuper_connections is decremented when db is denied
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
+ERROR 42000: Access denied for user 'test_user'@'localhost' to database 'bogus_db'
 connection default;
 connect  con$i, localhost, test_user,,test;
 connect  con$i, localhost, test_user,,test;

mysql-test/t/max_nonsuper_connections.test

@@ -99,6 +99,17 @@ while ($i)
   dec $i;
 }
 
+# Verify counter leak is fixed when permission to a database is denied
+--echo Verifying nonsuper_connections is decremented when db is denied
+--disable_query_log
+--let $i = 20
+--while ($i) {
+  --error ER_DBACCESS_DENIED_ERROR
+  --connect (con_denied_$i, localhost, test_user,,bogus_db)
+  --dec $i
+--}
+--enable_query_log
+
 # able to refill up max_nonsuper_connections
 connection default;
 let $i = 10;