fix(runtime): interop memory-safety fixes from the worker memory-corruption hunt - #458
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The collection adapters attached an ObjCDataWrapper to their JS object unconditionally, and DisposeValue's ObjCObject branch releases the adapter with the wrapper pointer cached in a local -- the adapter's -dealloc, running inside that release, freed the same wrapper the tail then deleted again. The double-free's recycled chunk corrupted live allocations (captured in the field as a registered persistent's slot word zeroed while its node stayed armed), surfacing as three distinct GC crash signatures on worker isolates within seconds of heavy collection marshalling. Ownership is now single and explicit: a JS object's internal field holds at most one wrapper and owns it; the first adapter to attach wins, a later one stays detached and never writes or clears the field; dataWrapper_ is a claim token for recognising our own wrapper, not an ownership handle. Every path that runs arbitrary code between reading the field and freeing it -- DisposeValue's tail and __releaseNativeCounterpart -- re-reads the field and frees only a wrapper still attached. DictionaryAdapter also gains the object_->Reset() the other adapters already had (its absence leaked the armed global-handle node), and its key enumerators retain the adapter -- NSEnumerator semantics -- so the reset cannot empty the persistent under a live enumeration. New GCFinalizerTests specs pin the ownership contract under the production workload mix (adapter marshalling interleaved with native TextDecoder/atob churn, finalizer-driven releases, a worker-isolate variant); they are tripwires -- the old double-free needs a guard-malloc/ASan lane to abort deterministically. Suite 1512/0.
A callee writes *error only on failure, so on success the read-back found whatever the malloc chunk last held. A non-null stale value was then sent localizedDescription and -- read through a __strong pointer -- retained and released by ARC: an over-release of whatever object now lives at that address, prematurely freeing live allocations whose owners keep writing through dangling references. Those writes landing in recycled GC bookkeeping produced the worker-isolate crash family this branch chases; under MallocScribble the stale read reproduces deterministically at boot as an unrecognized-selector throw on the scribble pattern. The other transient interop buffers are fully written before any read; this was the only uninitialized read-back.
Crash reports previously showed every worker as an anonymous NSOperationQueue thread; the thread name now carries the worker id and script basename (worker3:pixelmap-socket.js).
The adapter's persistent pins the JS object, not its bytes: a postMessage transfer detaches the ArrayBuffer and hands the store to another isolate, whose GC can free the memory while native code still holds this NSData — an async reader/writer then touches a freed, recycled chunk. Holding the BackingStore shared_ptr keeps the bytes alive for the adapter's lifetime, which is the contract NSData callers assume, and lets -bytes answer without unlocked cross-thread V8 access. The never-materialized-view branch now serves one stable copy freed in dealloc instead of leaking a fresh malloc per call.
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Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe runtime now preserves foreign JavaScript wrappers, cleans up only owned wrappers, pins ChangesAdapter lifecycle safety
NSError buffer initialization
Worker thread naming
Block wrapper lifecycle
Metadata initialization
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR hardens adapter disposal, error handling, backing-store lifetime, worker cleanup, and crash observability. No actionable merge-blocking risk remains beyond normal checks and review. Suggested reviewers: Poem
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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In `@NativeScript/runtime/NSDataAdapter.mm`:
- Around line 37-48: Update the NSDataAdapter initialization flow around the
ArrayBuffer and ArrayBufferView handling to capture the source byte length
before any transfer or detachment, and store that snapshot in the adapter.
Change length to return the captured value instead of querying ByteLength() on
the persistent source object, while preserving the existing backing-store and
byte-offset behavior.
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NativeScript/runtime/ArrayAdapter.mmNativeScript/runtime/DictionaryAdapter.mmNativeScript/runtime/Interop.mmNativeScript/runtime/NSDataAdapter.mmNativeScript/runtime/ObjectManager.mmNativeScript/runtime/Worker.mmTestRunner/app/tests/GCFinalizerTests.jsTestRunner/app/tests/adapterChurnWorker.js
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NSData is immutable — length must not change for the object's lifetime — but the live ByteLength() read reported zero after a transfer detach while the pinned bytes stayed valid, and it was also the adapter's last unlocked cross-thread V8 access.
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Inline comments:
In `@NativeScript/runtime/NSDataAdapter.mm`:
- Around line 96-103: Move on-heap ArrayBufferView materialization out of the
lazy -bytes fallback and perform it during initialization while the V8 isolate
is owned, using the existing isolate-validity and persistent-object flow. Update
-bytes and -mutableBytes to return only the completed native heap storage,
ensuring allocation and copy completion occur before publication; if lazy
materialization must remain, initialize the allocation and synchronize access so
detached or partial copies cannot be returned.
Apply the same fix in `@NativeScript/runtime/NSDataAdapter.mm` around lines 93 -
101: The isolate-validity ordering issue is part of the same stable-copy
lifetime and access contract.
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The lazy first--bytes copy ran isolate APIs from whatever thread the caller was on, could race concurrent callers on the publication, and a view detached before the first call would expose an uninitialized allocation. Copying during init — isolate owned, view alive — removes the lazy path entirely, so every -bytes branch answers from native storage.
An adapter released after its isolate died skipped the whole cleanup block and orphaned its attached wrapper — one 48-byte leak per adapter on every worker teardown. With the isolate gone the JS object and every other reader or deleter of the claim are gone too (all IsValid-gated), so the owner can free it unconditionally.
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Inline comments:
In `@NativeScript/runtime/ArrayAdapter.mm`:
- Around line 132-139: Prevent double deletion of dataWrapper_ when
__releaseNativeCounterpart retires the wrapper before adapter dealloc. In
ArrayAdapter.mm lines 132-139, DictionaryAdapter.mm lines 379-386, and
NSDataAdapter.mm lines 122-129, add shared claim-state tracking or adapter
invalidation so dealloc deletes the wrapper only while its claim remains live;
otherwise clear or skip the stale pointer.
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…ction Passing a JS function as a block argument caches a BlockWrapper on the function so repeat calls reuse the same block. That wrapper was freed only from the JSBlock dispose helper, and only by looking it up through the cached function -- which needs a live isolate. A block built on a worker isolate that outlives it, or released after it, skipped that branch entirely and orphaned the wrapper: two 48-byte tns::BlockWrapper leaks per TestRunner run, both allocated under WorkerWrapper::BackgroundLooper (NativeCallbackWorker and TeardownCrashWorker install an NSNotificationCenter observer block at module load). The block now carries the wrapper pointer, so disposal frees it without the isolate, and native code holding the block keeps the wrapper reachable in the meantime. While the isolate is alive the wrapper is freed only when the function's slot still points at it, the same ownership rule ObjectManager::DisposeValue applies -- __releaseNativeCounterpart can retire the same wrapper first. Disposal stays inline and callback_->Reset() stays unconditional.
…dInClass Freeing the loser is unsafe (never-initialized instance of an arbitrary class, arbitrary thread) and parking it merely converts the leak into perpetual retention; the leak stays, visible and explained, tracked by issue #459.
__releaseNativeCounterpart could delete an adapter's attached claim while a native reference kept the adapter alive; if the isolate then died before the adapter's -dealloc, the teardown branch freed the stale pointer again. Claims are now marked and retirement paths leave them attached — the only deleter is the adapter's own -dealloc, in either isolate state.
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Summary
Memory-safety fixes and hardening that came out of a production memory-corruption hunt (crashes at
global-handles.ccdrain CHECKs,DisposeValuesegfaults, and silent stalls in a worker-heavy app). The investigation root-caused four distinct defects; three were runtime bugs and are fixed here. The fourth — the one producing the headline crashes — turned out to be app/core-side:NSData.dataWithBytesNoCopy(ptr, len)(2-arg =freeWhenDone:YES) called over pointers into V8-owned ArrayBuffer backing buffers, handing Foundation ownership of memory the ArrayBufferSweeper also frees — a double-ownership double-free that sprays whatever allocation lands between the two frees. That is fixed by two NativeScript core patches (wgccryptogetRandomValues,file-system-accesswrite path); this PR carries the runtime's share: the fixes below plus observability that makes this bug class diagnosable.Fixes
Single-owner adapter wrappers and reentrancy-safe disposal.
DisposeValue's ObjCObject branch ran[target release]— which can re-enter through an adapter-deallocthat deletes the attached wrapper and resets the persistent — and then deleted the wrapper through a stale local: a double delete whose freed-chunk reuse corrupted unrelated allocations. The tail now re-reads the field after every reentrancy-capable step, and adapters only detach/free a wrapper that is still the one they attached. Also fixesDictionaryAdapternever resettingobject_(leaked armed weak nodes).Zero-initialized
NSErrorout-parameter buffer.Interop::CallFunctionInternalmalloc'd theNSError**slot without zeroing. Cocoa only writes*erroron failure, so every successful call read back heap garbage; a non-null garbage pointer went throughNSError* __strong*and got retained/released by ARC — an over-release of whatever live object had been reallocated at that address, freeing it under its true owner. Dates back to the originalNSError**support.NSDataAdapterpins its backing store. The adapter held aPersistent(pinning the JS object) but re-fetchedGetBackingStore()->Data()per-bytescall with no store reference — so apostMessagetransfer-detach could free the bytes while native code still held theNSData, and every call did unlocked cross-thread V8 access. The adapter now captures theshared_ptr<BackingStore>at init (bytes valid for the adapter's lifetime — the contract NSData callers assume) and-bytesno longer touches V8. The never-materialized-view branch, which leaked a freshmalloccopy on every call, now serves one stable copy freed indealloc.Adapters free their wrapper claim after isolate teardown. An adapter released after its isolate died (workers) skipped its whole cleanup block behind the
IsValid()gate and orphaned the attachedObjCDataWrapper— one 48-byte leak per adapter on every worker teardown, surfaced by this PR's new worker-churn test under Instruments. With the isolate gone, the JS object and every other reader or deleter of the claim are gone too (allIsValid-gated), so the owning adapter deletes it unconditionally. Verified with liveleaksruns: 24-per-adapter-type before, zero after.The
JSBlockowns the block cache attached to its function. Passing a JS function as a block argument caches aBlockWrapperon the function for block reuse; the dispose helper freed it only by looking it up through the cached function, which needs a live isolate — a block built on a worker isolate and released after its teardown orphaned the wrapper (two 48-byte leaks per TestRunner run). The block now carries its wrapper pointer, so disposal frees it without the isolate; while the isolate is alive the same slot-ownership rule asDisposeValueapplies, so__releaseNativeCounterpartcannot cause a double free. Disposal stays inline andcallback_->Reset()stays unconditional.Worker looper threads are named (
worker<id>:<script-basename>viapthread_setname_np). Every crash report now says which worker died instead of an anonymousNSOperationQueuethread — this single change converted the hunt's crash reports from anonymous to self-identifying.The forensic short version
The corruption presented as V8
global-handlesfatals on worker threads ("Finalizer callback must either reset its handle or re-arm it"), with the faulting values rotating between runs. Instrumented builds (registration-ordinal stamping, slot watches, guard pages, and finallyMallocStackLogging+ a pause-on-fatal park withmalloc_historyagainst the live task) produced the complete biography of one corrupted chunk:dataWithBytesNoCopy(ptr, len)on a pointer into that buffer → Foundation's small-payload path copies and frees the donor immediately;Persistent);Fixes 1 and 2 are real defects, found and validated during the hunt (fix 2's garbage read-back reproduced deterministically under
MallocScribble=1), but the final attribution run shows they were latent, not the production trigger: an unpatched released runtime with only the core call sites fixed soaked clean for 10+ minutes where every unpatched combination died in about a minute. The core double-free was the sole trigger; this PR removes the runtime's own members of the same premature-free bug class before they get their turn.Follow-ups (tracked, not in this PR)
dataWithBytesNoCopy:length:receives a pointer inside a live BackingStore — the metadata layer sees the selector, so this is checkable at the exact choke point and would have caught the core bugs in seconds.freeWhenDone-style APIs.MallocScribble/ ASan CI lane (MallocScribble=1deterministically caught fix 2 at boot).NSDataAdapter.mutableByteslength-uncoupling (setLength:/appendData:on an adapter can write past the store).Interop::GetResultcache-hit early-return skips the owned-result release (leak).MethodMeta::isImplementedInClassleaks the losing sample instance on re-entrant/racing cache population — kept visible and documented at the site rather than hidden (releasing a never-initialized instance of an arbitrary class is unsafe; parking it is perpetual retention): isImplementedInClass leaks the losing sample instance on re-entrant or racing cache population #459.xcodebuild cleanfails (a stray repo-rootbuild/dir shipped stale binaries three times during the hunt), and makebuild_npm_ios.shverifymetadata-generator/distfreshness — it packages whatever sits there, however stale, and the per-stage build flow (unlikebuild_all_ios.sh) never rebuilds it.Summary by CodeRabbit
Bug Fixes
Enhancements