From 9aaed75eea0145ef3ee88bdd6d5507e5fd8d76c2 Mon Sep 17 00:00:00 2001
From: lhofhansl <larsh@apache.org>
Date: Thu, 27 Oct 2022 19:31:42 -0700
Subject: [PATCH] Safety check the map's blocksize (#12895)

---
 src/content/subgames.cpp  | 2 ++
 src/serverenvironment.cpp | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/src/content/subgames.cpp b/src/content/subgames.cpp
index d0de926ef..3658fa83e 100644
--- a/src/content/subgames.cpp
+++ b/src/content/subgames.cpp
@@ -390,6 +390,8 @@ void loadGameConfAndInitWorld(const std::string &path, const std::string &name,
 		conf.set("mod_storage_backend", "sqlite3");
 		conf.setBool("creative_mode", g_settings->getBool("creative_mode"));
 		conf.setBool("enable_damage", g_settings->getBool("enable_damage"));
+		if (MAP_BLOCKSIZE != 16)
+			conf.set("blocksize", std::to_string(MAP_BLOCKSIZE));
 
 		if (!conf.updateConfigFile(worldmt_path.c_str())) {
 			throw BaseException("Failed to update the config file");
diff --git a/src/serverenvironment.cpp b/src/serverenvironment.cpp
index dfa3e0961..4cdb21a4b 100644
--- a/src/serverenvironment.cpp
+++ b/src/serverenvironment.cpp
@@ -420,6 +420,13 @@ void ServerEnvironment::init()
 
 	// If we open world.mt read the backend configurations.
 	if (succeeded) {
+		// Check that the world's blocksize matches the compiled MAP_BLOCKSIZE
+		u16 blocksize = 16;
+		conf.getU16NoEx("blocksize", blocksize);
+		if (blocksize != MAP_BLOCKSIZE) {
+			throw BaseException(std::string("The map's blocksize is not supported."));
+		}
+
 		// Read those values before setting defaults
 		bool player_backend_exists = conf.exists("player_backend");
 		bool auth_backend_exists = conf.exists("auth_backend");