Fix possible logical replication crash.

robertmhaas · robertmhaas · commit e7e7da2f8d57 · 2023-04-03T13:54:21.000-04:00
Commit c3afe8c added a new password_required option but forgot that you need database access to check whether an arbitrary role ID is a superuser. Report and patch by Hou Zhijie. I added a comment. Thanks to Alexander Lakhin for devising a way to reproduce the crash. Discussion: http://postgr.es/m/OS0PR01MB5716BFD7EC44284C89F40808948F9@OS0PR01MB5716.jpnprd01.prod.outlook.com
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
@@ -4545,12 +4545,14 @@ ApplyWorkerMain(Datum main_arg)
 		replorigin_session_setup(originid, 0);
 		replorigin_session_origin = originid;
 		origin_startpos = replorigin_session_get_progress(false);
-		CommitTransactionCommand();
 
 		/* Is the use of a password mandatory? */
 		must_use_password = MySubscription->passwordrequired &&
 			!superuser_arg(MySubscription->owner);
 
+		/* Note that the superuser_arg call can access the DB */
+		CommitTransactionCommand();
+
 		LogRepWorkerWalRcvConn = walrcv_connect(MySubscription->conninfo, true,
 												must_use_password,
 												MySubscription->name, &err);
