ffi: reject fast calls after library close

Optimized Fast API calls bypass InvokeFunction and can jump directly to
a symbol after DynamicLibrary::close() unloads its library.

Check the function's closed state in the AArch64 and SysV x64
trampolines before entering the target. If the library is closed,
schedule ERR_FFI_LIBRARY_CLOSED and return without calling the symbol.

Keep the JavaScript guard on platforms without a native trampoline guard
and for signatures that already require argument conversion or
validation. This keeps raw scalar fast calls close to their original
performance on supported platforms.

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: codex:gpt-5.6-sol

Author: trivikr

lib/ffi.js

@@ -68,6 +68,7 @@ const {
 } = require('internal/ffi-shared-buffer');
 
 const {
+  markFastLibraryClosed,
   wrapWithRawPointerConversions,
 } = require('internal/ffi/fast-api');
 
@@ -100,6 +101,27 @@ function wrapFFIFunction(rawFn, owner) {
 
 const rawGetFunction = DynamicLibrary.prototype.getFunction;
 const rawGetFunctions = DynamicLibrary.prototype.getFunctions;
+const rawClose = DynamicLibrary.prototype.close;
+
+function close() {
+  const result = FunctionPrototypeCall(rawClose, this);
+  markFastLibraryClosed(this);
+  return result;
+}
+
+ObjectDefineProperty(DynamicLibrary.prototype, 'close', {
+  __proto__: null,
+  configurable: true,
+  value: close,
+  writable: true,
+});
+
+ObjectDefineProperty(DynamicLibrary.prototype, SymbolDispose, {
+  __proto__: null,
+  configurable: true,
+  value: close,
+  writable: true,
+});
 
 DynamicLibrary.prototype.getFunction = function getFunction(name, signature) {
   const raw = FunctionPrototypeCall(rawGetFunction, this, name, signature);

lib/internal/errors.js

@@ -1234,6 +1234,7 @@ E('ERR_FEATURE_UNAVAILABLE_ON_PLATFORM',
   'The feature %s is unavailable on the current platform' +
   ', which is being used to run Node.js',
   TypeError);
+E('ERR_FFI_LIBRARY_CLOSED', 'Library is closed', Error);
 E('ERR_FS_CP_DIR_TO_NON_DIR',
   'Cannot overwrite non-directory with directory', SystemError);
 E('ERR_FS_CP_EEXIST', 'Target already exists', SystemError);

lib/internal/ffi/fast-api.js

@@ -5,6 +5,7 @@ const {
   NumberIsInteger,
   ObjectDefineProperty,
   ReflectApply,
+  SafeWeakMap,
   StringPrototypeIncludes,
   TypeError,
 } = primordials;
@@ -25,9 +26,16 @@ const {
   kFastBufferInvoke,
 } = internalBinding('ffi');
 
+const {
+  codes: {
+    ERR_FFI_LIBRARY_CLOSED,
+  },
+} = require('internal/errors');
+
 const U64_MAX = 0xFFFFFFFFFFFFFFFFn;
 const I64_MAX = 0x7FFFFFFFFFFFFFFFn;
 const I64_MIN = -0x8000000000000000n;
+const fastLibraryStates = new SafeWeakMap();
 
 // These ranges mirror ToFFIArgument in src/ffi/types.cc. V8's Fast API
 // exposes narrow integers as 32-bit values and uses truncating BigInt
@@ -202,7 +210,20 @@ function inheritMetadata(wrapper, rawFn, nargs) {
   return wrapper;
 }
 
-function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
+function markFastLibraryClosed(owner) {
+  const state = fastLibraryStates.get(owner);
+  if (state !== undefined) {
+    state.closed = true;
+  }
+}
+
+function throwIfFastLibraryClosed(state) {
+  if (state.closed) {
+    throw new ERR_FFI_LIBRARY_CLOSED();
+  }
+}
+
+function wrapWithRawPointerConversions(rawFn, argumentTypes, owner) {
   if (rawFn === undefined || rawFn === null) {
     return rawFn;
   }
@@ -213,11 +234,14 @@ function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
     return rawFn;
   }
 
-  const indexes = getFastArgumentIndexes(argumentTypes);
-  if (indexes === null) {
-    return rawFn;
+  let state = fastLibraryStates.get(owner);
+  if (state === undefined) {
+    state = { __proto__: null, closed: false };
+    fastLibraryStates.set(owner, state);
   }
 
+  const indexes = getFastArgumentIndexes(argumentTypes) ?? [];
+
   const stringState = {
     __proto__: null,
     buffers: [],
@@ -233,6 +257,7 @@ function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
     const fastBufferInvoke = needsPointerLikeConversion(t0) ?
       rawFn[kFastBufferInvoke] : undefined;
     wrapper = function(a0) {
+      throwIfFastLibraryClosed(state);
       if (arguments.length !== 1) {
         throwFFIArgCountError(1, arguments.length);
       }
@@ -262,6 +287,7 @@ function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
     const t0 = argumentTypes[0];
     const t1 = argumentTypes[1];
     wrapper = function(a0, a1) {
+      throwIfFastLibraryClosed(state);
       if (arguments.length !== 2) {
         throwFFIArgCountError(2, arguments.length);
       }
@@ -283,6 +309,7 @@ function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
     const t1 = argumentTypes[1];
     const t2 = argumentTypes[2];
     wrapper = function(a0, a1, a2) {
+      throwIfFastLibraryClosed(state);
       if (arguments.length !== 3) {
         throwFFIArgCountError(3, arguments.length);
       }
@@ -300,6 +327,7 @@ function wrapWithRawPointerConversions(rawFn, argumentTypes, _owner) {
     };
   } else {
     wrapper = function(...args) {
+      throwIfFastLibraryClosed(state);
       if (args.length !== nargs) {
         throwFFIArgCountError(nargs, args.length);
       }
@@ -332,5 +360,6 @@ module.exports = {
   convertPointerArg,
   hasPointerMemoryArg,
   hasStringPointerArg,
+  markFastLibraryClosed,
   wrapWithRawPointerConversions,
 };

src/ffi/fast.cc

@@ -247,6 +247,12 @@ extern "C" uintptr_t node_ffi_fast_buffer_data(v8::Local<v8::Value> value,
   return kInvalidBuffer;
 }
 
+extern "C" void node_ffi_fast_library_closed(v8::Isolate* isolate) {
+  if (isolate != nullptr) {
+    THROW_ERR_FFI_LIBRARY_CLOSED(isolate);
+  }
+}
+
 FastFFIMetadata::~FastFFIMetadata() {
   // Metadata owns executable memory through `trampoline`; releasing it here
   // ties code lifetime to the V8 function's weak FFIFunctionInfo cleanup.
@@ -265,7 +271,18 @@ bool IsFastCallSupported() {
 #endif
 }
 
-std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn) {
+bool IsFastLibraryGuardSupported() {
+#if defined(__aarch64__) || defined(_M_ARM64) ||                               \
+    (defined(__x86_64__) && !defined(_WIN32))
+  return true;
+#else
+  return false;
+#endif
+}
+
+std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn,
+                                                       const bool* closed,
+                                                       v8::Isolate* isolate) {
   // Bail early if executable memory allocation doesn't work on this process
   // (missing MAP_JIT entitlement, hardened runtime, SELinux execmem, etc.).
   // The self-test runs once and caches the result.
@@ -299,6 +316,7 @@ std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn) {
   std::vector<FastFFIType> args;
   args.reserve(fn.arg_type_names.size());
   bool needs_bigint = NeedsBigIntRepresentation(result);
+  const bool guards_library = IsFastLibraryGuardSupported();
   bool needs_callback_options = false;
   // Normalize public argument names into FastFFIType values while collecting
   // signature-wide flags required by V8 CFunctionInfo.
@@ -320,8 +338,9 @@ std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn) {
   // The platform-specific trampoline is the executable entrypoint V8 calls.
   // If the platform rejects the signature, the whole fast metadata object is
   // discarded and the caller chooses another invocation path.
+  FastFFITrampolineConfig config{fn.ptr, closed, isolate};
   if (!node_ffi_create_fast_trampoline(
-          fn.ptr, args.data(), args.size(), result, &metadata->trampoline)) {
+          config, args.data(), args.size(), result, &metadata->trampoline)) {
     return nullptr;
   }
 
@@ -348,6 +367,7 @@ std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn) {
                    : CFunctionInfo::Int64Representation::kNumber);
   metadata->c_function =
       v8::CFunction(metadata->trampoline.code, metadata->c_function_info.get());
+  metadata->guards_library = guards_library;
   return metadata;
 }
 

src/ffi/fast.h

@@ -36,6 +36,12 @@ struct FastFFITrampoline {
   size_t size = 0;
 };
 
+struct FastFFITrampolineConfig {
+  void* target;
+  const bool* closed;
+  v8::Isolate* isolate;
+};
+
 struct FastFFIMetadata {
   FastFFIMetadata() = default;
   ~FastFFIMetadata();
@@ -47,6 +53,7 @@ struct FastFFIMetadata {
   std::vector<v8::CTypeInfo> arg_info;
   std::unique_ptr<v8::CFunctionInfo> c_function_info;
   v8::CFunction c_function;
+  bool guards_library = false;
 };
 
 // Public detection queries.
@@ -56,6 +63,7 @@ struct FastFFIMetadata {
 // of any particular signature — if this returns false, no signature can
 // use the fast-call path.
 bool IsFastCallSupported();
+bool IsFastLibraryGuardSupported();
 
 bool SignatureNeedsRawPointerConversions(const FFIFunction& fn);
 bool SignatureNeedsFastIntegerValidation(const FFIFunction& fn);
@@ -65,19 +73,23 @@ std::shared_ptr<FFIFunction> CloneWithRawPointerArgNames(
     const std::shared_ptr<FFIFunction>& fn);
 std::shared_ptr<FFIFunction> CloneWithFastBufferArgNames(
     const std::shared_ptr<FFIFunction>& fn);
-std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn);
+std::unique_ptr<FastFFIMetadata> CreateFastFFIMetadata(const FFIFunction& fn,
+                                                       const bool* closed,
+                                                       v8::Isolate* isolate);
 
 }  // namespace node::ffi
 
 extern "C" {
 uintptr_t node_ffi_fast_buffer_data(v8::Local<v8::Value> value,
                                     v8::FastApiCallbackOptions* options,
                                     uint32_t index);
-bool node_ffi_create_fast_trampoline(void* target,
-                                     const node::ffi::FastFFIType* args,
-                                     size_t argc,
-                                     node::ffi::FastFFIType result,
-                                     node::ffi::FastFFITrampoline* out);
+void node_ffi_fast_library_closed(v8::Isolate* isolate);
+bool node_ffi_create_fast_trampoline(
+    const node::ffi::FastFFITrampolineConfig& config,
+    const node::ffi::FastFFIType* args,
+    size_t argc,
+    node::ffi::FastFFIType result,
+    node::ffi::FastFFITrampoline* out);
 void node_ffi_free_fast_trampoline(node::ffi::FastFFITrampoline* trampoline);
 }
 

src/ffi/platforms/arm64.cc

@@ -81,6 +81,14 @@ uint32_t LdrXSp(unsigned reg, unsigned offset) {
   return 0xf94003e0 | ((offset / 8) << 10) | reg;
 }
 
+uint32_t LdrbW(unsigned dst, unsigned base) {
+  return 0x39400000 | (base << 5) | dst;
+}
+
+uint32_t CbzW(unsigned reg, unsigned instruction_offset) {
+  return 0x34000000 | ((instruction_offset & 0x7ffff) << 5) | reg;
+}
+
 uint32_t MovzW(unsigned dst, uint16_t value) {
   // Load a small immediate into a W register. The buffer helper's argument
   // index is uint32_t, but current Fast API signatures are capped well below
@@ -213,14 +221,15 @@ bool ProtectCode(void* code, size_t code_size) {
 }  // namespace
 
 extern "C" bool node_ffi_create_fast_trampoline(
-    void* target,
+    const node::ffi::FastFFITrampolineConfig& config,
     const node::ffi::FastFFIType* args,
     size_t argc,
     node::ffi::FastFFIType result,
     node::ffi::FastFFITrampoline* out) {
   // Null inputs mean the caller cannot safely create executable code for this
   // signature. Report rejection so the generic FFI path can be used instead.
-  if (target == nullptr || out == nullptr) {
+  if (config.target == nullptr || config.closed == nullptr ||
+      config.isolate == nullptr || out == nullptr) {
     return false;
   }
 
@@ -275,6 +284,24 @@ extern "C" bool node_ffi_create_fast_trampoline(
   // call can return through this generated trampoline safely.
   *cursor++ = kStpFpLrPreIndex;
 
+  // Fast calls bypass DynamicLibrary::InvokeFunction, so check the stable
+  // FFIFunction::closed flag before touching the target address. The open
+  // branch is the hot path. On close, schedule the standard JS exception and
+  // return; V8 checks for pending exceptions after Fast API calls.
+  EmitLoadX16(&cursor, reinterpret_cast<uintptr_t>(config.closed));
+  *cursor++ = LdrbW(17, 16);
+  uint32_t* open_branch = cursor++;
+  EmitLoadX16(&cursor, reinterpret_cast<uintptr_t>(config.isolate));
+  *cursor++ = MovX(0, 16);
+  EmitLoadX16(
+      &cursor, reinterpret_cast<uintptr_t>(node_ffi_fast_library_closed));
+  *cursor++ = kBlrX16;
+  *cursor++ = MovX(0, 31);
+  *cursor++ = kLdpFpLrPostIndex;
+  *cursor++ = kRet;
+  *open_branch =
+      CbzW(17, static_cast<unsigned>(cursor - open_branch));
+
   if (has_buffer_args) {
     // Buffer conversion calls a C++ helper before the target call, so spill all
     // incoming GP registers that may be clobbered by that helper.
@@ -361,7 +388,7 @@ extern "C" bool node_ffi_create_fast_trampoline(
 
   // Tail of the trampoline: load the actual library symbol address and call it
   // with arguments now arranged according to the native ABI.
-  EmitLoadX16(&cursor, reinterpret_cast<uintptr_t>(target));
+  EmitLoadX16(&cursor, reinterpret_cast<uintptr_t>(config.target));
   *cursor++ = kBlrX16;
 
   if (has_buffer_args) {
@@ -414,7 +441,7 @@ extern "C" void node_ffi_free_fast_trampoline(
     !(defined(__riscv) && __riscv_xlen == 64) && !defined(__s390x__)
 
 extern "C" bool node_ffi_create_fast_trampoline(
-    void* target,
+    const node::ffi::FastFFITrampolineConfig& config,
     const node::ffi::FastFFIType* args,
     size_t argc,
     node::ffi::FastFFIType result,

src/ffi/platforms/loong64.cc

@@ -74,12 +74,12 @@ void FreeCode(void* code, size_t code_size) {
 }  // namespace
 
 extern "C" bool node_ffi_create_fast_trampoline(
-    void* target,
+    const node::ffi::FastFFITrampolineConfig& config,
     const node::ffi::FastFFIType* args,
     size_t argc,
     node::ffi::FastFFIType result,
     node::ffi::FastFFITrampoline* out) {
-  if (target == nullptr || out == nullptr || IsNarrowType(result)) {
+  if (config.target == nullptr || out == nullptr || IsNarrowType(result)) {
     return false;
   }
 
@@ -126,7 +126,7 @@ extern "C" bool node_ffi_create_fast_trampoline(
   Emit32(&cursor, LdD(12, 12, 16));     // ld.d t0, t0, literal
   Emit32(&cursor, Jirl(0, 12, 0));      // jr t0
   Emit32(&cursor, Or(0, 0, 0));         // nop; align literal to 8 bytes
-  Emit64(&cursor, reinterpret_cast<uintptr_t>(target));
+  Emit64(&cursor, reinterpret_cast<uintptr_t>(config.target));
 
   const size_t written = reinterpret_cast<uint8_t*>(cursor) -
                          static_cast<uint8_t*>(code);

src/ffi/platforms/ppc64.cc

@@ -86,12 +86,12 @@ void FreeCode(void* code, size_t code_size) {
 }  // namespace
 
 extern "C" bool node_ffi_create_fast_trampoline(
-    void* target,
+    const node::ffi::FastFFITrampolineConfig& config,
     const node::ffi::FastFFIType* args,
     size_t argc,
     node::ffi::FastFFIType result,
     node::ffi::FastFFITrampoline* out) {
-  if (target == nullptr || out == nullptr || IsNarrowType(result)) {
+  if (config.target == nullptr || out == nullptr || IsNarrowType(result)) {
     return false;
   }
 
@@ -149,7 +149,7 @@ extern "C" bool node_ffi_create_fast_trampoline(
   if (gp_count % 2 == 0) {
     Emit32(&cursor, 0x60000000);  // nop; align literal to 8 bytes
   }
-  Emit64(&cursor, reinterpret_cast<uintptr_t>(target));
+  Emit64(&cursor, reinterpret_cast<uintptr_t>(config.target));
 
   const size_t written = reinterpret_cast<uint8_t*>(cursor) -
                          static_cast<uint8_t*>(code);
@@ -179,7 +179,7 @@ extern "C" void node_ffi_free_fast_trampoline(
 #else
 
 extern "C" bool node_ffi_create_fast_trampoline(
-    void* target,
+    const node::ffi::FastFFITrampolineConfig& config,
     const node::ffi::FastFFIType* args,
     size_t argc,
     node::ffi::FastFFIType result,