node-api: fix shutdown crashes

Refs: nodejs/node-addon-api#906 Ensure that finalization is not defered during shutdown. The env for the addon is deleted immediately after iterating the list of finalizers to be run. Defering causes crashes as the finalization uses the already deleted env. Signed-off-by: Michael Dawson <[email protected]> PR-URL: #38492 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Chengzhong Wu <[email protected]> Reviewed-By: Gabriel Schulhof <[email protected]>
nodejs · May 30, 2021 · 5ed4b9d · 5ed4b9d
1 parent 9a2945f
commit 5ed4b9d
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Showing 2 changed files with 38 additions and 2 deletions.
diff --git a/src/js_native_api_v8.h b/src/js_native_api_v8.h
@@ -122,6 +122,37 @@ struct napi_env__ {
   void* instance_data = nullptr;
 };
 
+// This class is used to keep a napi_env live in a way that
+// is exception safe versus calling Ref/Unref directly
+class EnvRefHolder {
+ public:
+  explicit EnvRefHolder(napi_env env) : _env(env) {
+      _env->Ref();
+  }
+
+  explicit EnvRefHolder(const EnvRefHolder& other): _env(other.env()) {
+    _env->Ref();
+  }
+
+  EnvRefHolder(EnvRefHolder&& other) {
+    _env = other._env;
+    other._env = nullptr;
+  }
+
+  ~EnvRefHolder() {
+    if (_env != nullptr) {
+      _env->Unref();
+    }
+  }
+
+  napi_env env(void) const {
+    return _env;
+  }
+
+ private:
+  napi_env _env;
+};
+
 static inline napi_status napi_clear_last_error(napi_env env) {
   env->last_error.error_code = napi_ok;
 

diff --git a/src/node_api.cc b/src/node_api.cc
@@ -37,8 +37,13 @@ struct node_napi_env__ : public napi_env__ {
   }
 
   void CallFinalizer(napi_finalize cb, void* data, void* hint) override {
-    napi_env env = static_cast<napi_env>(this);
-    node_env()->SetImmediate([=](node::Environment* node_env) {
+    // we need to keep the env live until the finalizer has been run
+    // EnvRefHolder provides an exception safe wrapper to Ref and then
+    // Unref once the lamba is freed
+    EnvRefHolder liveEnv(static_cast<napi_env>(this));
+    node_env()->SetImmediate([=, liveEnv = std::move(liveEnv)]
+        (node::Environment* node_env) {
+      napi_env env = liveEnv.env();
       v8::HandleScope handle_scope(env->isolate);
       v8::Context::Scope context_scope(env->context());
       env->CallIntoModule([&](napi_env env) {