From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Fri, 27 Dec 2019 09:42:26 -0800
Subject: [PATCH] Guard against serializing mismatching chunk coordinate

Should help if something dumb happens

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 be67dc16bf70e4517efd213ca9002f116f60b57c..6c28a611b9b79c3322ab07883972c07b3bfc3073 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
@@ -67,6 +67,13 @@ public class ChunkSerializer {
 
     private static final Logger LOGGER = LogManager.getLogger();
 
+    // Paper start - guard against serializing mismatching coordinates
+    // TODO Note: This needs to be re-checked each update
+    public static ChunkPos getChunkCoordinate(CompoundTag chunkData) {
+        CompoundTag levelData = chunkData.getCompound("Level");
+        return new ChunkPos(levelData.getInt("xPos"), levelData.getInt("zPos"));
+    }
+    // Paper end
     // Paper start
     public static final class InProgressChunkHolder {
 
@@ -92,8 +99,8 @@ public class ChunkSerializer {
         // Paper end
         ChunkGenerator chunkgenerator = worldserver.getChunkSource().getGenerator();
         BiomeSource worldchunkmanager = chunkgenerator.getBiomeSource();
-        CompoundTag nbttagcompound1 = nbttagcompound.getCompound("Level");
-        ChunkPos chunkcoordintpair1 = new ChunkPos(nbttagcompound1.getInt("xPos"), nbttagcompound1.getInt("zPos"));
+        CompoundTag nbttagcompound1 = nbttagcompound.getCompound("Level"); // Paper - diff on change, see ChunkRegionLoader#getChunkCoordinate
+        ChunkPos chunkcoordintpair1 = new ChunkPos(nbttagcompound1.getInt("xPos"), nbttagcompound1.getInt("zPos")); // Paper - diff on change, see ChunkRegionLoader#getChunkCoordinate
 
         if (!Objects.equals(chunkcoordintpair, chunkcoordintpair1)) {
             ChunkSerializer.LOGGER.error("Chunk file at {} is in the wrong location; relocating. (Expected {}, got {})", chunkcoordintpair, chunkcoordintpair, chunkcoordintpair1);
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
index 684442b7175e30b6d4cafb2f7d2d4c10517cc33d..1af804c5c6fb2b20ea3f020610763c1d7dcee110 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
@@ -13,6 +13,7 @@ import net.minecraft.SharedConstants;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.NbtUtils;
 import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerChunkCache;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.util.datafix.DataFixTypes;
@@ -119,6 +120,13 @@ public class ChunkStorage implements AutoCloseable {
 
     public void write(ChunkPos chunkcoordintpair, CompoundTag nbttagcompound) throws IOException { write(chunkcoordintpair, nbttagcompound); } // Paper OBFHELPER
     public void write(ChunkPos chunkcoordintpair, CompoundTag nbttagcompound) throws IOException { // Paper - OBFHELPER - (Switched around for safety)
+        // Paper start
+        if (!chunkcoordintpair.equals(ChunkSerializer.getChunkCoordinate(nbttagcompound))) {
+            String world = (this instanceof ChunkMap) ? ((ChunkMap)this).level.getWorld().getName() : null;
+            throw new IllegalArgumentException("Chunk coordinate and serialized data do not have matching coordinates, trying to serialize coordinate " + chunkcoordintpair.toString()
+                + " but compound says coordinate is " + ChunkSerializer.getChunkCoordinate(nbttagcompound).toString() + (world == null ? " for an unknown world" : (" for world: " + world)));
+        }
+        // Paper end
         this.regionFileCache.write(chunkcoordintpair, nbttagcompound);
         if (this.legacyStructureHandler != null) {
             synchronized (this.persistentDataLock) { // Paper - Async chunk loading