From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Zach Brown <zach@zachbr.io>
Date: Tue, 23 Jul 2019 20:44:47 -0500
Subject: [PATCH] Do not let the server load chunks from newer versions

If the server attempts to load a chunk generated by a newer version of
the game, immediately stop the server to prevent data corruption.

You can override this functionality at your own peril.

diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
index 1f95ac18990822a64f0bb2af947693c4b88cdf73..6b7d3433c6e26888b3c718cfe13237342ad9b2b4 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
@@ -98,10 +98,25 @@ public class ChunkSerializer {
         holder.tasks.forEach(Runnable::run);
         return holder.protoChunk;
     }
+
+    // Paper start
+    private static final int CURRENT_DATA_VERSION = SharedConstants.getCurrentVersion().getWorldVersion();
+    private static final boolean JUST_CORRUPT_IT = Boolean.getBoolean("Paper.ignoreWorldDataVersion");
+    // Paper end
+
     public static InProgressChunkHolder loadChunk(ServerLevel world, StructureManager structureManager, PoiManager poiStorage, ChunkPos pos, CompoundTag nbt, boolean distinguish) {
         java.util.ArrayDeque<Runnable> tasksToExecuteOnMain = new java.util.ArrayDeque<>();
         // Paper end
         ChunkGenerator chunkgenerator = world.getChunkSource().getGenerator();
+        // Paper start - Do NOT attempt to load chunks saved with newer versions
+        if (nbt.contains("DataVersion", 99)) {
+            int dataVersion = nbt.getInt("DataVersion");
+            if (!JUST_CORRUPT_IT && dataVersion > CURRENT_DATA_VERSION) {
+                new RuntimeException("Server attempted to load chunk saved with newer version of minecraft! " + dataVersion + " > " + CURRENT_DATA_VERSION).printStackTrace();
+                System.exit(1);
+            }
+        }
+        // Paper end
         BiomeSource worldchunkmanager = chunkgenerator.getBiomeSource();
         CompoundTag nbttagcompound1 = nbt.getCompound("Level"); // Paper - diff on change, see ChunkSerializer#getChunkCoordinate
         ChunkPos chunkcoordintpair1 = new ChunkPos(nbttagcompound1.getInt("xPos"), nbttagcompound1.getInt("zPos")); // Paper - diff on change, see ChunkSerializer#getChunkCoordinate