n-api: unlink reference during its destructor

Gabriel Schulhof · danielleadams · commit 9b6512f7ded1 · 2020-11-09T13:34:56.000-05:00
Currently, a reference is being unlinked from the list of references tracked by the environment when `v8impl::Reference::Delete` is called. This causes a leak when deletion must be deferred because the finalizer hasn't yet run, but the finalizer does not run because environment teardown is in progress, and so no more gc runs will happen, and the `FinalizeAll` run that happens during environment teardown does not catch the reference because it's no longer in the list. The test below will fail when running with ASAN: ``` ./node ./test/node-api/test_worker_terminate_finalization/test.js ``` OTOH if, to address the above leak, we make a special case to not unlink a reference during environment teardown, we run into a situation where the reference gets deleted by `v8impl::Reference::Delete` but does not get unlinked because it's environment teardown time. This leaves a stale pointer in the linked list which will result in a use-after-free in `FinalizeAll` during environment teardown. The test below will fail if we make the above change: ``` ./node -e "require('./test/node-api/test_instance_data/build/Release/test_ref_then_set.node');" ``` Thus, we unlink a reference precisely when we destroy it – in its destructor. Refs: #34731 Refs: #34839 Refs: #35620 Refs: #35777 Fixes: #35778 Signed-off-by: Gabriel Schulhof <gabriel.schulhof@intel.com> PR-URL: #35933 Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Michael Dawson <midawson@redhat.com> Reviewed-By: Zeyu Yang <himself65@outlook.com>
diff --git a/src/js_native_api_v8.cc b/src/js_native_api_v8.cc
@@ -220,6 +220,8 @@ class RefBase : protected Finalizer, RefTracker {
                        finalize_hint);
   }
 
+  virtual ~RefBase() { Unlink(); }
+
   inline void* Data() {
     return _finalize_data;
   }
@@ -240,7 +242,6 @@ class RefBase : protected Finalizer, RefTracker {
   // the finalizer and _delete_self is set. In this case we
   // know we need to do the deletion so just do it.
   static inline void Delete(RefBase* reference) {
-    reference->Unlink();
     if ((reference->RefCount() != 0) ||
         (reference->_delete_self) ||
         (reference->_finalize_ran)) {
diff --git a/test/node-api/test_worker_terminate_finalization/test.js b/test/node-api/test_worker_terminate_finalization/test.js
@@ -1,11 +1,9 @@
 'use strict';
 const common = require('../../common');
 
-// TODO(addaleax): Run this test once it stops failing under ASAN/valgrind.
 // Refs: https://github.com/nodejs/node/issues/34731
 // Refs: https://github.com/nodejs/node/pull/35777
 // Refs: https://github.com/nodejs/node/issues/35778
-common.skip('Reference management in N-API leaks memory');
 
 const { Worker, isMainThread } = require('worker_threads');
 
