From 5161bfd916603c9f4b61d3553565fe0d8f4e744b 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/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 40704664b..e1944774c 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -2075,6 +2075,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
     }
 
     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 {
-- 
2.20.1