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module: use symbol in WeakMap to manage host defined options
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Previously when managing the importModuleDynamically callback of
vm.compileFunction(), we use an ID number as the host defined option
and maintain a per-Environment ID -> CompiledFnEntry map to retain
the top-level referrer function returned by vm.compileFunction() in
order to pass it back to the callback, but it would leak because with
how we used v8::Persistent to maintain this reference, V8 would not
be able to understand the cycle and would just think that the
CompiledFnEntry was supposed to live forever. We made an attempt
to make that reference known to V8 by making the CompiledFnEntry weak
and using a private symbol to make CompiledFnEntry strongly
references the top-level referrer function in
nodejs#46785, but that turned out to be
unsound, because the there's no guarantee that the top-level function
must be alive while import() can still be initiated from that
function, since V8 could discard the top-level function and only keep
inner functions alive, so relying on the top-level function to keep
the CompiledFnEntry alive could result in use-after-free which caused
a revert of that fix.

With this patch we use a symbol in the host defined options instead of
a number, because with the stage-3 symbol-as-weakmap-keys proposal
we could directly use that symbol to keep the referrer alive using a
WeakMap. As a bonus this also keeps the other kinds of referrers
alive as long as import() can still be initiated from that
Script/Module, so this also fixes the long-standing crash caused by
vm.Script being GC'ed too early when its importModuleDynamically
callback still needs it.

PR-URL: nodejs#48510
Refs: nodejs#44211
Refs: nodejs#42080
Refs: nodejs#47096
Refs: nodejs#43205
Refs: nodejs#38695
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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joyeecheung committed Sep 26, 2023
1 parent 92ba261 commit 7aae66a
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Showing 16 changed files with 185 additions and 188 deletions.
5 changes: 3 additions & 2 deletions lib/internal/modules/esm/create_dynamic_module.js
Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,9 @@ import.meta.done();

if (imports.length)
reflect.imports = { __proto__: null };
const { setCallbackForWrap } = require('internal/modules/esm/utils');
setCallbackForWrap(m, {
const { registerModule } = require('internal/modules/esm/utils');
registerModule(m, {
__proto__: null,
initializeImportMeta: (meta, wrap) => {
meta.exports = reflect.exports;
if (reflect.imports)
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5 changes: 3 additions & 2 deletions lib/internal/modules/esm/loader.js
Original file line number Diff line number Diff line change
Expand Up @@ -180,9 +180,10 @@ class ModuleLoader {
) {
const evalInstance = (url) => {
const { ModuleWrap } = internalBinding('module_wrap');
const { setCallbackForWrap } = require('internal/modules/esm/utils');
const { registerModule } = require('internal/modules/esm/utils');
const module = new ModuleWrap(url, undefined, source, 0, 0);
setCallbackForWrap(module, {
registerModule(module, {
__proto__: null,
initializeImportMeta: (meta, wrap) => this.importMetaInitialize(meta, { url }),
importModuleDynamically: (specifier, { url }, importAssertions) => {
return this.import(specifier, url, importAssertions);
Expand Down
5 changes: 3 additions & 2 deletions lib/internal/modules/esm/translators.js
Original file line number Diff line number Diff line change
Expand Up @@ -116,8 +116,9 @@ translators.set('module', async function moduleStrategy(url, source, isMain) {
maybeCacheSourceMap(url, source);
debug(`Translating StandardModule ${url}`);
const module = new ModuleWrap(url, undefined, source, 0, 0);
const { setCallbackForWrap } = require('internal/modules/esm/utils');
setCallbackForWrap(module, {
const { registerModule } = require('internal/modules/esm/utils');
registerModule(module, {
__proto__: null,
initializeImportMeta: (meta, wrap) => this.importMetaInitialize(meta, { url }),
importModuleDynamically,
});
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87 changes: 69 additions & 18 deletions lib/internal/modules/esm/utils.js
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,11 @@ const {
ObjectFreeze,
} = primordials;

const {
privateSymbols: {
host_defined_option_symbol,
},
} = internalBinding('util');
const {
ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING,
ERR_INVALID_ARG_VALUE,
Expand All @@ -21,16 +26,8 @@ const {
setImportModuleDynamicallyCallback,
setInitializeImportMetaObjectCallback,
} = internalBinding('module_wrap');
const {
getModuleFromWrap,
} = require('internal/vm/module');
const assert = require('internal/assert');

const callbackMap = new SafeWeakMap();
function setCallbackForWrap(wrap, data) {
callbackMap.set(wrap, data);
}

let defaultConditions;
function getDefaultConditions() {
assert(defaultConditions !== undefined);
Expand Down Expand Up @@ -73,21 +70,75 @@ function getConditionsSet(conditions) {
return getDefaultConditionsSet();
}

function initializeImportMetaObject(wrap, meta) {
if (callbackMap.has(wrap)) {
const { initializeImportMeta } = callbackMap.get(wrap);
/**
* @callback ImportModuleDynamicallyCallback
* @param {string} specifier
* @param {ModuleWrap|ContextifyScript|Function|vm.Module} callbackReferrer
* @param {object} assertions
* @returns { Promise<void> }
*/

/**
* @callback InitializeImportMetaCallback
* @param {object} meta
* @param {ModuleWrap|ContextifyScript|Function|vm.Module} callbackReferrer
*/

/**
* @typedef {{
* callbackReferrer: ModuleWrap|ContextifyScript|Function|vm.Module
* initializeImportMeta? : InitializeImportMetaCallback,
* importModuleDynamically? : ImportModuleDynamicallyCallback
* }} ModuleRegistry
*/

/**
* @type {WeakMap<symbol, ModuleRegistry>}
*/
const moduleRegistries = new SafeWeakMap();

/**
* V8 would make sure that as long as import() can still be initiated from
* the referrer, the symbol referenced by |host_defined_option_symbol| should
* be alive, which in term would keep the settings object alive through the
* WeakMap, and in turn that keeps the referrer object alive, which would be
* passed into the callbacks.
* The reference goes like this:
* [v8::internal::Script] (via host defined options) ----1--> [idSymbol]
* [callbackReferrer] (via host_defined_option_symbol) ------2------^ |
* ^----------3---- (via WeakMap)------
* 1+3 makes sure that as long as import() can still be initiated, the
* referrer wrap is still around and can be passed into the callbacks.
* 2 is only there so that we can get the id symbol to configure the
* weak map.
* @param {ModuleWrap|ContextifyScript|Function} referrer The referrer to
* get the id symbol from. This is different from callbackReferrer which
* could be set by the caller.
* @param {ModuleRegistry} registry
*/
function registerModule(referrer, registry) {
const idSymbol = referrer[host_defined_option_symbol];
// To prevent it from being GC'ed.
registry.callbackReferrer ??= referrer;
moduleRegistries.set(idSymbol, registry);
}

// The native callback
function initializeImportMetaObject(symbol, meta) {
if (moduleRegistries.has(symbol)) {
const { initializeImportMeta, callbackReferrer } = moduleRegistries.get(symbol);
if (initializeImportMeta !== undefined) {
meta = initializeImportMeta(meta, getModuleFromWrap(wrap) || wrap);
meta = initializeImportMeta(meta, callbackReferrer);
}
}
}

async function importModuleDynamicallyCallback(wrap, specifier, assertions) {
if (callbackMap.has(wrap)) {
const { importModuleDynamically } = callbackMap.get(wrap);
// The native callback
async function importModuleDynamicallyCallback(symbol, specifier, assertions) {
if (moduleRegistries.has(symbol)) {
const { importModuleDynamically, callbackReferrer } = moduleRegistries.get(symbol);
if (importModuleDynamically !== undefined) {
return importModuleDynamically(
specifier, getModuleFromWrap(wrap) || wrap, assertions);
return importModuleDynamically(specifier, callbackReferrer, assertions);
}
}
throw new ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING();
Expand Down Expand Up @@ -151,7 +202,7 @@ async function initializeHooks() {
}

module.exports = {
setCallbackForWrap,
registerModule,
initializeESM,
initializeHooks,
getDefaultConditions,
Expand Down
7 changes: 4 additions & 3 deletions lib/internal/vm.js
Original file line number Diff line number Diff line change
Expand Up @@ -100,9 +100,10 @@ function internalCompileFunction(code, params, options) {
const { importModuleDynamicallyWrap } = require('internal/vm/module');
const wrapped = importModuleDynamicallyWrap(importModuleDynamically);
const func = result.function;
const { setCallbackForWrap } = require('internal/modules/esm/utils');
setCallbackForWrap(result.cacheKey, {
importModuleDynamically: (s, _k, i) => wrapped(s, func, i),
const { registerModule } = require('internal/modules/esm/utils');
registerModule(func, {
__proto__: null,
importModuleDynamically: wrapped,
});
}

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16 changes: 9 additions & 7 deletions lib/internal/vm/module.js
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,6 @@ const {
ObjectSetPrototypeOf,
ReflectApply,
SafePromiseAllReturnVoid,
SafeWeakMap,
Symbol,
SymbolToStringTag,
TypeError,
Expand Down Expand Up @@ -69,7 +68,6 @@ const STATUS_MAP = {

let globalModuleId = 0;
const defaultModuleName = 'vm:module';
const wrapToModuleMap = new SafeWeakMap();

const kWrap = Symbol('kWrap');
const kContext = Symbol('kContext');
Expand Down Expand Up @@ -120,25 +118,30 @@ class Module {
});
}

let registry = { __proto__: null };
if (sourceText !== undefined) {
this[kWrap] = new ModuleWrap(identifier, context, sourceText,
options.lineOffset, options.columnOffset,
options.cachedData);
const { setCallbackForWrap } = require('internal/modules/esm/utils');
setCallbackForWrap(this[kWrap], {
registry = {
__proto__: null,
initializeImportMeta: options.initializeImportMeta,
importModuleDynamically: options.importModuleDynamically ?
importModuleDynamicallyWrap(options.importModuleDynamically) :
undefined,
});
};
} else {
assert(syntheticEvaluationSteps);
this[kWrap] = new ModuleWrap(identifier, context,
syntheticExportNames,
syntheticEvaluationSteps);
}

wrapToModuleMap.set(this[kWrap], this);
// This will take precedence over the referrer as the object being
// passed into the callbacks.
registry.callbackReferrer = this;
const { registerModule } = require('internal/modules/esm/utils');
registerModule(this[kWrap], registry);

this[kContext] = context;
}
Expand Down Expand Up @@ -445,5 +448,4 @@ module.exports = {
SourceTextModule,
SyntheticModule,
importModuleDynamicallyWrap,
getModuleFromWrap: (wrap) => wrapToModuleMap.get(wrap),
};
5 changes: 3 additions & 2 deletions lib/vm.js
Original file line number Diff line number Diff line change
Expand Up @@ -105,8 +105,9 @@ class Script extends ContextifyScript {
validateFunction(importModuleDynamically,
'options.importModuleDynamically');
const { importModuleDynamicallyWrap } = require('internal/vm/module');
const { setCallbackForWrap } = require('internal/modules/esm/utils');
setCallbackForWrap(this, {
const { registerModule } = require('internal/modules/esm/utils');
registerModule(this, {
__proto__: null,
importModuleDynamically:
importModuleDynamicallyWrap(importModuleDynamically),
});
Expand Down
10 changes: 0 additions & 10 deletions src/env-inl.h
Original file line number Diff line number Diff line change
Expand Up @@ -393,16 +393,6 @@ inline AliasedInt32Array& Environment::stream_base_state() {
return stream_base_state_;
}

inline uint32_t Environment::get_next_module_id() {
return module_id_counter_++;
}
inline uint32_t Environment::get_next_script_id() {
return script_id_counter_++;
}
inline uint32_t Environment::get_next_function_id() {
return function_id_counter_++;
}

ShouldNotAbortOnUncaughtScope::ShouldNotAbortOnUncaughtScope(
Environment* env)
: env_(env) {
Expand Down
8 changes: 0 additions & 8 deletions src/env.h
Original file line number Diff line number Diff line change
Expand Up @@ -746,14 +746,6 @@ class Environment : public MemoryRetainer {
builtins::BuiltinLoader* builtin_loader();

std::unordered_multimap<int, loader::ModuleWrap*> hash_to_module_map;
std::unordered_map<uint32_t, loader::ModuleWrap*> id_to_module_map;
std::unordered_map<uint32_t, contextify::ContextifyScript*>
id_to_script_map;
std::unordered_map<uint32_t, contextify::CompiledFnEntry*> id_to_function_map;

inline uint32_t get_next_module_id();
inline uint32_t get_next_script_id();
inline uint32_t get_next_function_id();

EnabledDebugList* enabled_debug_list() { return &enabled_debug_list_; }

Expand Down
2 changes: 1 addition & 1 deletion src/env_properties.h
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
V(arrow_message_private_symbol, "node:arrowMessage") \
V(contextify_context_private_symbol, "node:contextify:context") \
V(decorated_private_symbol, "node:decorated") \
V(host_defined_option_symbol, "node:host_defined_option_symbol") \
V(napi_type_tag, "node:napi:type_tag") \
V(napi_wrapper, "node:napi:wrapper") \
V(untransferable_object_private_symbol, "node:untransferableObject") \
Expand Down Expand Up @@ -338,7 +339,6 @@
V(blocklist_constructor_template, v8::FunctionTemplate) \
V(contextify_global_template, v8::ObjectTemplate) \
V(contextify_wrapper_template, v8::ObjectTemplate) \
V(compiled_fn_entry_template, v8::ObjectTemplate) \
V(crypto_key_object_handle_constructor, v8::FunctionTemplate) \
V(env_proxy_template, v8::ObjectTemplate) \
V(env_proxy_ctor_template, v8::FunctionTemplate) \
Expand Down
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