fs: fix use after free in stat watcher

The uv_fs_poll_t handle was stopped but not closed, leaving libuv's internal
handle queue in a corrupted state.

src/node_stat_watcher.cc

@@ -49,19 +49,39 @@ void StatWatcher::Initialize(Handle<Object> target) {
 }
 
 
+static void Delete(uv_handle_t* handle) {
+  delete reinterpret_cast<uv_fs_poll_t*>(handle);
+}
+
+
+StatWatcher::StatWatcher()
+  : ObjectWrap()
+  , watcher_(new uv_fs_poll_t)
+{
+  uv_fs_poll_init(uv_default_loop(), watcher_);
+  watcher_->data = static_cast<void*>(this);
+}
+
+
+StatWatcher::~StatWatcher() {
+  Stop();
+  uv_close(reinterpret_cast<uv_handle_t*>(watcher_), Delete);
+}
+
+
 void StatWatcher::Callback(uv_fs_poll_t* handle,
                            int status,
                            const uv_statbuf_t* prev,
                            const uv_statbuf_t* curr) {
-  StatWatcher* wrap = container_of(handle, StatWatcher, watcher_);
+  StatWatcher* wrap = static_cast<StatWatcher*>(handle->data);
-  assert(handle == &wrap->watcher_);
+  assert(wrap->watcher_ == handle);
   HandleScope scope;
   Local<Value> argv[3];
   argv[0] = BuildStatsObject(curr);
   argv[1] = BuildStatsObject(prev);
   argv[2] = Integer::New(status);
   if (status == -1) {
-    SetErrno(uv_last_error(wrap->watcher_.loop));
+    SetErrno(uv_last_error(wrap->watcher_->loop));
   }
   if (onchange_sym.IsEmpty()) {
     onchange_sym = NODE_PSYMBOL("onchange");
@@ -88,8 +108,8 @@ Handle<Value> StatWatcher::Start(const Arguments& args) {
   const bool persistent = args[1]->BooleanValue();
   const uint32_t interval = args[2]->Uint32Value();
 
-  if (!persistent) uv_unref(reinterpret_cast<uv_handle_t*>(&wrap->watcher_));
+  if (!persistent) uv_unref(reinterpret_cast<uv_handle_t*>(wrap->watcher_));
-  uv_fs_poll_start(&wrap->watcher_, Callback, *path, interval);
+  uv_fs_poll_start(wrap->watcher_, Callback, *path, interval);
   wrap->Ref();
 
   return Undefined();
@@ -109,8 +129,8 @@ Handle<Value> StatWatcher::Stop(const Arguments& args) {
 
 
 void StatWatcher::Stop () {
-  if (!uv_is_active(reinterpret_cast<uv_handle_t*>(&watcher_))) return;
+  if (!uv_is_active(reinterpret_cast<uv_handle_t*>(watcher_))) return;
-  uv_fs_poll_stop(&watcher_);
+  uv_fs_poll_stop(watcher_);
   Unref();
 }
 

src/node_stat_watcher.h

@@ -34,13 +34,8 @@ class StatWatcher : ObjectWrap {
  protected:
   static v8::Persistent<v8::FunctionTemplate> constructor_template;
 
-  StatWatcher() : ObjectWrap() {
+  StatWatcher();
-    uv_fs_poll_init(uv_default_loop(), &watcher_);
+  virtual ~StatWatcher();
-  }
-
-  ~StatWatcher() {
-    Stop();
-  }
 
   static v8::Handle<v8::Value> New(const v8::Arguments& args);
   static v8::Handle<v8::Value> Start(const v8::Arguments& args);
@@ -53,7 +48,7 @@ class StatWatcher : ObjectWrap {
                        const uv_statbuf_t* curr);
   void Stop();
 
-  uv_fs_poll_t watcher_;
+  uv_fs_poll_t* watcher_;
 };
 
 }  // namespace node