Paper/patches/server/0123-Don-t-allow-entities-to-ride-themselves-572.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Alfie Cleveland <alfeh@me.com>
Date: Sun, 8 Jan 2017 04:31:36 +0000
Subject: [PATCH] Don't allow entities to ride themselves - #572


diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 5a6aa26ee937a456ede56a9b18cf3bf58aba892d..081a95e3bb448a44565f6e75ebbc18bbc5fe1b18 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2240,6 +2240,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
     }
 
     protected boolean addPassenger(Entity entity) { // CraftBukkit
+        if (entity == this) throw new IllegalArgumentException("Entities cannot become a passenger of themselves"); // Paper - issue 572
         if (entity.getVehicle() != this) {
             throw new IllegalStateException("Use x.startRiding(y), not y.addPassenger(x)");
         } else {