src: set thread local env in CreateEnvironment

This commit set the Environment as a thread local when CreateEnvironment
is called which is currently not being done. This would lead to a
segment fault if later node::AtExit is called without specifying the
environment parameter. This specific issue was reported by Electron.

If I recall correctly, back when this was implemented the motivation was
that if embedders have multiple environments per isolate they should be
using the AtExit functions that take an environment. This is not the
case with Electron which only create a single environment (as far as I
know), and if a native module calls AtExit this would lead to the
segment fault.

I was able to reproduce Electron issue and the provided test simulates
it. I was also able to use this patch and verify that it works for the
Electron issue as well.

PR-URL: #18573
Refs: #9163
Refs: electron/electron#11299
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Matheus Marchini <[email protected]>

src/env-inl.h

@@ -311,6 +311,10 @@ inline Environment* Environment::GetCurrent(
       info.Data().template As<v8::External>()->Value());
 }
 
+inline Environment* Environment::GetThreadLocalEnv() {
+  return static_cast<Environment*>(uv_key_get(&thread_local_env));
+}
+
 inline Environment::Environment(IsolateData* isolate_data,
                                 v8::Local<v8::Context> context)
     : isolate_(context->GetIsolate()),

src/env.cc

@@ -80,6 +80,11 @@ v8::CpuProfiler* IsolateData::GetCpuProfiler() {
   return cpu_profiler_;
 }
 
+
+void InitThreadLocalOnce() {
+  CHECK_EQ(0, uv_key_create(&Environment::thread_local_env));
+}
+
 void Environment::Start(int argc,
                         const char* const* argv,
                         int exec_argc,
@@ -147,6 +152,10 @@ void Environment::Start(int argc,
 
   SetupProcessObject(this, argc, argv, exec_argc, exec_argv);
   LoadAsyncWrapperInfo(this);
+
+  static uv_once_t init_once = UV_ONCE_INIT;
+  uv_once(&init_once, InitThreadLocalOnce);
+  uv_key_set(&thread_local_env, this);
 }
 
 void Environment::CleanupHandles() {
@@ -471,4 +480,6 @@ void Environment::AsyncHooks::grow_async_ids_stack() {
       async_ids_stack_.GetJSArray()).FromJust();
 }
 
+uv_key_t Environment::thread_local_env = {};
+
 }  // namespace node

src/env.h

@@ -564,6 +564,9 @@ class Environment {
   static inline Environment* GetCurrent(
       const v8::PropertyCallbackInfo<T>& info);
 
+  static uv_key_t thread_local_env;
+  static inline Environment* GetThreadLocalEnv();
+
   inline Environment(IsolateData* isolate_data, v8::Local<v8::Context> context);
   inline ~Environment();
 

src/node.cc

@@ -4207,11 +4207,8 @@ uv_loop_t* GetCurrentEventLoop(v8::Isolate* isolate) {
 }
 
 
-static uv_key_t thread_local_env;
-
-
 void AtExit(void (*cb)(void* arg), void* arg) {
-  auto env = static_cast<Environment*>(uv_key_get(&thread_local_env));
+  auto env = Environment::GetThreadLocalEnv();
   AtExit(env, cb, arg);
 }
 
@@ -4342,8 +4339,6 @@ inline int Start(Isolate* isolate, IsolateData* isolate_data,
   Local<Context> context = NewContext(isolate);
   Context::Scope context_scope(context);
   Environment env(isolate_data, context);
-  CHECK_EQ(0, uv_key_create(&thread_local_env));
-  uv_key_set(&thread_local_env, &env);
   env.Start(argc, argv, exec_argc, exec_argv, v8_is_profiling);
 
   const char* path = argc > 1 ? argv[1] : nullptr;
@@ -4393,7 +4388,6 @@ inline int Start(Isolate* isolate, IsolateData* isolate_data,
 
   const int exit_code = EmitExit(&env);
   RunAtExit(&env);
-  uv_key_delete(&thread_local_env);
 
   v8_platform.DrainVMTasks(isolate);
   v8_platform.CancelVMTasks(isolate);

test/cctest/test_environment.cc

@@ -33,6 +33,16 @@ TEST_F(EnvironmentTest, AtExitWithEnvironment) {
   EXPECT_TRUE(called_cb_1);
 }
 
+TEST_F(EnvironmentTest, AtExitWithoutEnvironment) {
+  const v8::HandleScope handle_scope(isolate_);
+  const Argv argv;
+  Env env {handle_scope, argv};
+
+  AtExit(at_exit_callback1);  // No Environment is passed to AtExit.
+  RunAtExit(*env);
+  EXPECT_TRUE(called_cb_1);
+}
+
 TEST_F(EnvironmentTest, AtExitWithArgument) {
   const v8::HandleScope handle_scope(isolate_);
   const Argv argv;