From 5be786c804d36e9950598a01cf39f05574af2acc Mon Sep 17 00:00:00 2001
From: MetaDucky <metaducky AT gmail DOT com>
Date: Wed, 20 Nov 2013 22:11:57 +0100
Subject: Fixed potential NULL pointer and leak when setting node metadata

---
 src/map.cpp                       | 19 ++++++++-----------
 src/map.h                         | 17 ++++++++++++++++-
 src/rollback_interface.cpp        |  8 +++++++-
 src/script/lua_api/l_nodemeta.cpp | 18 ++++++++++++------
 src/script/lua_api/l_nodemeta.h   | 13 +++++++++++++
 5 files changed, 56 insertions(+), 19 deletions(-)

diff --git a/src/map.cpp b/src/map.cpp
index 0dbfd42f4..0f9c82c3c 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -2279,7 +2279,7 @@ void Map::transformLiquids(std::map<v3s16, MapBlock*> & modified_blocks)
 	updateLighting(lighting_modified_blocks, modified_blocks);
 }
 
-NodeMetadata* Map::getNodeMetadata(v3s16 p)
+NodeMetadata *Map::getNodeMetadata(v3s16 p)
 {
 	v3s16 blockpos = getNodeBlockPos(p);
 	v3s16 p_rel = p - blockpos*MAP_BLOCKSIZE;
@@ -2289,8 +2289,7 @@ NodeMetadata* Map::getNodeMetadata(v3s16 p)
 				<<PP(blockpos)<<std::endl;
 		block = emergeBlock(blockpos, false);
 	}
-	if(!block)
-	{
+	if(!block){
 		infostream<<"WARNING: Map::getNodeMetadata(): Block not found"
 				<<std::endl;
 		return NULL;
@@ -2299,7 +2298,7 @@ NodeMetadata* Map::getNodeMetadata(v3s16 p)
 	return meta;
 }
 
-void Map::setNodeMetadata(v3s16 p, NodeMetadata *meta)
+bool Map::setNodeMetadata(v3s16 p, NodeMetadata *meta)
 {
 	v3s16 blockpos = getNodeBlockPos(p);
 	v3s16 p_rel = p - blockpos*MAP_BLOCKSIZE;
@@ -2309,13 +2308,13 @@ void Map::setNodeMetadata(v3s16 p, NodeMetadata *meta)
 				<<PP(blockpos)<<std::endl;
 		block = emergeBlock(blockpos, false);
 	}
-	if(!block)
-	{
+	if(!block){
 		infostream<<"WARNING: Map::setNodeMetadata(): Block not found"
 				<<std::endl;
-		return;
+		return false;
 	}
 	block->m_node_metadata.set(p_rel, meta);
+	return true;
 }
 
 void Map::removeNodeMetadata(v3s16 p)
@@ -2342,8 +2341,7 @@ NodeTimer Map::getNodeTimer(v3s16 p)
 				<<PP(blockpos)<<std::endl;
 		block = emergeBlock(blockpos, false);
 	}
-	if(!block)
-	{
+	if(!block){
 		infostream<<"WARNING: Map::getNodeTimer(): Block not found"
 				<<std::endl;
 		return NodeTimer();
@@ -2362,8 +2360,7 @@ void Map::setNodeTimer(v3s16 p, NodeTimer t)
 				<<PP(blockpos)<<std::endl;
 		block = emergeBlock(blockpos, false);
 	}
-	if(!block)
-	{
+	if(!block){
 		infostream<<"WARNING: Map::setNodeTimer(): Block not found"
 				<<std::endl;
 		return;
diff --git a/src/map.h b/src/map.h
index a6480c569..8e55af437 100644
--- a/src/map.h
+++ b/src/map.h
@@ -307,7 +307,22 @@ public:
 	*/
 
 	NodeMetadata* getNodeMetadata(v3s16 p);
-	void setNodeMetadata(v3s16 p, NodeMetadata *meta);
+
+	/**
+	 * Sets metadata for a node.
+	 * This method sets the metadata for a given node.
+	 * On success, it returns @c true and the object pointed to
+	 * by @p meta is then managed by the system and should
+	 * not be deleted by the caller.
+	 *
+	 * In case of failure, the method returns @c false and the
+	 * caller is still responsible for deleting the object!
+	 *
+	 * @param p node coordinates
+	 * @param meta pointer to @c NodeMetadata object
+	 * @return @c true on success, false on failure
+	 */
+	bool setNodeMetadata(v3s16 p, NodeMetadata *meta);
 	void removeNodeMetadata(v3s16 p);
 
 	/*
diff --git a/src/rollback_interface.cpp b/src/rollback_interface.cpp
index 70a9e9457..808b07fed 100644
--- a/src/rollback_interface.cpp
+++ b/src/rollback_interface.cpp
@@ -340,7 +340,13 @@ bool RollbackAction::applyRevert(Map *map, InventoryManager *imgr, IGameDef *gam
 				if(n_old.meta != ""){
 					if(!meta){
 						meta = new NodeMetadata(gamedef);
-						map->setNodeMetadata(p, meta);
+						if(!map->setNodeMetadata(p, meta)){
+							delete meta;
+							infostream<<"RollbackAction::applyRevert(): "
+									<<"setNodeMetadata failed at "
+									<<PP(p)<<" for "<<n_old.name<<std::endl;
+							return false;
+						}
 					}
 					std::istringstream is(n_old.meta, std::ios::binary);
 					meta->deSerialize(is);
diff --git a/src/script/lua_api/l_nodemeta.cpp b/src/script/lua_api/l_nodemeta.cpp
index f9c8794d5..4f20e56f9 100644
--- a/src/script/lua_api/l_nodemeta.cpp
+++ b/src/script/lua_api/l_nodemeta.cpp
@@ -42,10 +42,12 @@ NodeMetaRef* NodeMetaRef::checkobject(lua_State *L, int narg)
 NodeMetadata* NodeMetaRef::getmeta(NodeMetaRef *ref, bool auto_create)
 {
 	NodeMetadata *meta = ref->m_env->getMap().getNodeMetadata(ref->m_p);
-	if(meta == NULL && auto_create)
-	{
+	if(meta == NULL && auto_create)	{
 		meta = new NodeMetadata(ref->m_env->getGameDef());
-		ref->m_env->getMap().setNodeMetadata(ref->m_p, meta);
+		if(!ref->m_env->getMap().setNodeMetadata(ref->m_p, meta)) {
+			delete meta;
+			return NULL;
+		}
 	}
 	return meta;
 }
@@ -227,17 +229,21 @@ int NodeMetaRef::l_from_table(lua_State *L)
 	NodeMetaRef *ref = checkobject(L, 1);
 	int base = 2;
 
+	// clear old metadata first
+	ref->m_env->getMap().removeNodeMetadata(ref->m_p);
+
 	if(lua_isnil(L, base)){
 		// No metadata
-		ref->m_env->getMap().removeNodeMetadata(ref->m_p);
 		lua_pushboolean(L, true);
 		return 1;
 	}
 
-	// Has metadata; clear old one first
-	ref->m_env->getMap().removeNodeMetadata(ref->m_p);
 	// Create new metadata
 	NodeMetadata *meta = getmeta(ref, true);
+	if(meta == NULL){
+		lua_pushboolean(L, false);
+		return 1;
+	}
 	// Set fields
 	lua_getfield(L, base, "fields");
 	int fieldstable = lua_gettop(L);
diff --git a/src/script/lua_api/l_nodemeta.h b/src/script/lua_api/l_nodemeta.h
index ed06ff0fa..e39ac3931 100644
--- a/src/script/lua_api/l_nodemeta.h
+++ b/src/script/lua_api/l_nodemeta.h
@@ -39,6 +39,19 @@ private:
 
 	static NodeMetaRef *checkobject(lua_State *L, int narg);
 
+	/**
+	 * Retrieve metadata for a node.
+	 * If @p auto_create is set and the specified node has no metadata information
+	 * associated with it yet, the method attempts to attach a new metadata object
+	 * to the node and returns a pointer to the metadata when successful.
+	 *
+	 * However, it is NOT guaranteed that the method will return a pointer,
+	 * and @c NULL may be returned in case of an error regardless of @p auto_create.
+	 *
+	 * @param ref specifies the node for which the associated metadata is retrieved.
+	 * @param auto_create when true, try to create metadata information for the node if it has none.
+	 * @return pointer to a @c NodeMetadata object or @c NULL in case of error.
+	 */
 	static NodeMetadata* getmeta(NodeMetaRef *ref, bool auto_create);
 
 	static void reportMetadataChange(NodeMetaRef *ref);
-- 
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