From 16f6d7e7ab5bf2f2cc9b3266b39baf214c186ec2 Mon Sep 17 00:00:00 2001
From: Joyee Cheung <joyeec9h3@gmail.com>
Date: Wed, 22 Feb 2023 20:30:59 +0100
Subject: [PATCH] vm: fix leak in vm.compileFunction when
 importModuleDynamically is used

Previously in the implementation there was a cycle that V8 could not
detect:

Strong global reference to CompiledFnEntry (JS wrapper)
    -> strong reference to callback setting (through the
       callbackMap key-value pair)
    -> importModuleDynamically (wrapper in internalCompileFunction())
    -> Strong reference to the compiled function (through closure in
       internalCompileFunction())

The CompiledFnEntry only gets GC'ed when the compiled function is GC'ed.
Since the compiled function is always reachable as described above,
there is a leak.

We only needed the first strong global reference because we didn't want
the function to outlive the CompiledFnEntry. In this case it can be
solved by using a private symbol instead of going with the global
reference + destruction in the weak callback, which V8's GC is not
going to understand.

PR-URL: https://github.com/nodejs/node/pull/46785
Fixes: https://github.com/nodejs/node/issues/42080
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
---
 src/env_properties.h                         |  1 +
 src/node_contextify.cc                       | 17 +++++------------
 src/node_contextify.h                        |  3 ---
 test/pummel/test-vm-compile-function-leak.js | 14 ++++++++++++++
 4 files changed, 20 insertions(+), 15 deletions(-)
 create mode 100644 test/pummel/test-vm-compile-function-leak.js

diff --git a/src/env_properties.h b/src/env_properties.h
index 623e3022856989..7553823a9be48a 100644
--- a/src/env_properties.h
+++ b/src/env_properties.h
@@ -20,6 +20,7 @@
 #define PER_ISOLATE_PRIVATE_SYMBOL_PROPERTIES(V)                               \
   V(arrow_message_private_symbol, "node:arrowMessage")                         \
   V(contextify_context_private_symbol, "node:contextify:context")              \
+  V(compiled_function_entry, "node:compiled_function_entry")                   \
   V(decorated_private_symbol, "node:decorated")                                \
   V(napi_type_tag, "node:napi:type_tag")                                       \
   V(napi_wrapper, "node:napi:wrapper")                                         \
diff --git a/src/node_contextify.cc b/src/node_contextify.cc
index d618dafcb5f14d..2a4d4618dbd2a3 100644
--- a/src/node_contextify.cc
+++ b/src/node_contextify.cc
@@ -77,7 +77,6 @@ using v8::Uint32;
 using v8::UnboundScript;
 using v8::Value;
 using v8::WeakCallbackInfo;
-using v8::WeakCallbackType;
 
 // The vm module executes code in a sandboxed environment with a different
 // global object than the rest of the code. This is achieved by applying
@@ -1263,8 +1262,7 @@ void ContextifyContext::CompileFunction(
            context).ToLocal(&cache_key)) {
     return;
   }
-  CompiledFnEntry* entry = new CompiledFnEntry(env, cache_key, id, fn);
-  env->id_to_function_map.emplace(id, entry);
+  new CompiledFnEntry(env, cache_key, id, fn);
 
   Local<Object> result = Object::New(isolate);
   if (result->Set(parsing_context, env->function_string(), fn).IsNothing())
@@ -1296,23 +1294,18 @@ void ContextifyContext::CompileFunction(
   args.GetReturnValue().Set(result);
 }
 
-void CompiledFnEntry::WeakCallback(
-    const WeakCallbackInfo<CompiledFnEntry>& data) {
-  CompiledFnEntry* entry = data.GetParameter();
-  delete entry;
-}
-
 CompiledFnEntry::CompiledFnEntry(Environment* env,
                                  Local<Object> object,
                                  uint32_t id,
                                  Local<Function> fn)
-    : BaseObject(env, object), id_(id), fn_(env->isolate(), fn) {
-  fn_.SetWeak(this, WeakCallback, v8::WeakCallbackType::kParameter);
+    : BaseObject(env, object), id_(id) {
+  MakeWeak();
+  fn->SetPrivate(env->context(), env->compiled_function_entry(), object);
+  env->id_to_function_map.emplace(id, this);
 }
 
 CompiledFnEntry::~CompiledFnEntry() {
   env()->id_to_function_map.erase(id_);
-  fn_.ClearWeak();
 }
 
 static void StartSigintWatchdog(const FunctionCallbackInfo<Value>& args) {
diff --git a/src/node_contextify.h b/src/node_contextify.h
index 76c89318bb6cbf..a9b7741e61b2c2 100644
--- a/src/node_contextify.h
+++ b/src/node_contextify.h
@@ -194,9 +194,6 @@ class CompiledFnEntry final : public BaseObject {
 
  private:
   uint32_t id_;
-  v8::Global<v8::Function> fn_;
-
-  static void WeakCallback(const v8::WeakCallbackInfo<CompiledFnEntry>& data);
 };
 
 v8::Maybe<bool> StoreCodeCacheResult(
diff --git a/test/pummel/test-vm-compile-function-leak.js b/test/pummel/test-vm-compile-function-leak.js
new file mode 100644
index 00000000000000..465f300d4310d1
--- /dev/null
+++ b/test/pummel/test-vm-compile-function-leak.js
@@ -0,0 +1,14 @@
+'use strict';
+
+// Flags: --max-old-space-size=10
+
+require('../common');
+const vm = require('vm');
+
+const code = `console.log("${'hello world '.repeat(1e5)}");`;
+
+for (let i = 0; i < 10000; i++) {
+  vm.compileFunction(code, [], {
+    importModuleDynamically: () => {},
+  });
+}