From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jakob Kummerow <jkummerow@chromium.org>
Date: Tue, 24 Sep 2024 17:34:49 +0200
Subject: Properly check max module size

and allow d8-based tests for it.

Fixed: 368241697
Change-Id: Iddc9f7e669de7a1d79dccbc99bcc5fb43dad67a1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5886728
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Matthias Liedtke <mliedtke@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#96272}

diff --git a/src/wasm/streaming-decoder.cc b/src/wasm/streaming-decoder.cc
index 786c5aa250f055a0f69ca28403bfa679638e6465..9eb2d2fb9f1e973b04c8cf7829cc7b2849b632f9 100644
--- a/src/wasm/streaming-decoder.cc
+++ b/src/wasm/streaming-decoder.cc
@@ -294,6 +294,10 @@ void AsyncStreamingDecoder::Finish(bool can_use_compiled_module) {
   if (!full_wire_bytes_.back().empty()) {
     size_t total_length = 0;
     for (auto& bytes : full_wire_bytes_) total_length += bytes.size();
+    if (ok()) {
+      // {DecodeSectionLength} enforces this with graceful error reporting.
+      CHECK_LE(total_length, max_module_size());
+    }
     auto all_bytes = base::OwnedVector<uint8_t>::NewForOverwrite(total_length);
     uint8_t* ptr = all_bytes.begin();
     for (auto& bytes : full_wire_bytes_) {
@@ -627,6 +631,18 @@ std::unique_ptr<AsyncStreamingDecoder::DecodingState>
 AsyncStreamingDecoder::DecodeSectionLength::NextWithValue(
     AsyncStreamingDecoder* streaming) {
   TRACE_STREAMING("DecodeSectionLength(%zu)\n", value_);
+  // Check if this section fits into the overall module length limit.
+  // Note: {this->module_offset_} is the position of the section ID byte,
+  // {streaming->module_offset_} is the start of the section's payload (i.e.
+  // right after the just-decoded section length varint).
+  // The latter can already exceed the max module size, when the previous
+  // section barely fit into it, and this new section's ID or length crossed
+  // the threshold.
+  uint32_t payload_start = streaming->module_offset();
+  size_t max_size = max_module_size();
+  if (payload_start > max_size || max_size - payload_start < value_) {
+    return streaming->ToErrorState();
+  }
   SectionBuffer* buf =
       streaming->CreateNewBuffer(module_offset_, section_id_, value_,
                                  buffer().SubVector(0, bytes_consumed_));
diff --git a/src/wasm/wasm-engine.cc b/src/wasm/wasm-engine.cc
index 6b668b111c9d801e13f4d74f227c02029c4e80ec..8a3a855924fee296fd85e8b98d976e0c9f4c74c9 100644
--- a/src/wasm/wasm-engine.cc
+++ b/src/wasm/wasm-engine.cc
@@ -2009,10 +2009,11 @@ uint32_t max_table_init_entries() {
 
 // {max_module_size} is declared in wasm-limits.h.
 size_t max_module_size() {
-  // Clamp the value of --wasm-max-module-size between 16 and just below 2GB.
+  // Clamp the value of --wasm-max-module-size between 16 and the maximum
+  // that the implementation supports.
   constexpr size_t kMin = 16;
-  constexpr size_t kMax = RoundDown<kSystemPointerSize>(size_t{kMaxInt});
-  static_assert(kMin <= kV8MaxWasmModuleSize && kV8MaxWasmModuleSize <= kMax);
+  constexpr size_t kMax = kV8MaxWasmModuleSize;
+  static_assert(kMin <= kV8MaxWasmModuleSize);
   return std::clamp(v8_flags.wasm_max_module_size.value(), kMin, kMax);
 }
 
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index d8cff07657d4dd0e71a4c677b27e96fd67cd00a3..ae04f27efb30f2bf086bd4fe4bf9a3594c38c581 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -195,8 +195,8 @@ GET_FIRST_ARGUMENT_AS(Tag)
 #undef GET_FIRST_ARGUMENT_AS
 
 i::wasm::ModuleWireBytes GetFirstArgumentAsBytes(
-    const v8::FunctionCallbackInfo<v8::Value>& info, ErrorThrower* thrower,
-    bool* is_shared) {
+    const v8::FunctionCallbackInfo<v8::Value>& info, size_t max_length,
+    ErrorThrower* thrower, bool* is_shared) {
   DCHECK(i::ValidateCallbackInfo(info));
   const uint8_t* start = nullptr;
   size_t length = 0;
@@ -227,7 +227,6 @@ i::wasm::ModuleWireBytes GetFirstArgumentAsBytes(
   if (length == 0) {
     thrower->CompileError("BufferSource argument is empty");
   }
-  size_t max_length = i::wasm::max_module_size();
   if (length > max_length) {
     // The spec requires a CompileError for implementation-defined limits, see
     // https://webassembly.github.io/spec/js-api/index.html#limits.
@@ -624,7 +623,8 @@ void WebAssemblyCompileImpl(const v8::FunctionCallbackInfo<v8::Value>& info) {
       new AsyncCompilationResolver(isolate, context, promise_resolver));
 
   bool is_shared = false;
-  auto bytes = GetFirstArgumentAsBytes(info, &thrower, &is_shared);
+  auto bytes = GetFirstArgumentAsBytes(info, i::wasm::max_module_size(),
+                                       &thrower, &is_shared);
   if (thrower.error()) {
     resolver->OnCompilationFailed(thrower.Reify());
     return;
@@ -656,8 +656,11 @@ void WasmStreamingCallbackForTesting(
       v8::WasmStreaming::Unpack(info.GetIsolate(), info.Data());
 
   bool is_shared = false;
+  // We don't check the buffer length up front, to allow d8 to test that the
+  // streaming decoder implementation handles overly large inputs correctly.
+  size_t unlimited = std::numeric_limits<size_t>::max();
   i::wasm::ModuleWireBytes bytes =
-      GetFirstArgumentAsBytes(info, &thrower, &is_shared);
+      GetFirstArgumentAsBytes(info, unlimited, &thrower, &is_shared);
   if (thrower.error()) {
     streaming->Abort(Utils::ToLocal(thrower.Reify()));
     return;
@@ -759,7 +762,8 @@ void WebAssemblyValidateImpl(const v8::FunctionCallbackInfo<v8::Value>& info) {
   ErrorThrower thrower(i_isolate, "WebAssembly.validate()");
 
   bool is_shared = false;
-  auto bytes = GetFirstArgumentAsBytes(info, &thrower, &is_shared);
+  auto bytes = GetFirstArgumentAsBytes(info, i::wasm::max_module_size(),
+                                       &thrower, &is_shared);
 
   v8::ReturnValue<v8::Value> return_value = info.GetReturnValue();
 
@@ -838,7 +842,8 @@ void WebAssemblyModuleImpl(const v8::FunctionCallbackInfo<v8::Value>& info) {
   }
 
   bool is_shared = false;
-  auto bytes = GetFirstArgumentAsBytes(info, &thrower, &is_shared);
+  auto bytes = GetFirstArgumentAsBytes(info, i::wasm::max_module_size(),
+                                       &thrower, &is_shared);
 
   if (thrower.error()) {
     return;
@@ -1156,7 +1161,8 @@ void WebAssemblyInstantiateImpl(
   }
 
   bool is_shared = false;
-  auto bytes = GetFirstArgumentAsBytes(info, &thrower, &is_shared);
+  auto bytes = GetFirstArgumentAsBytes(info, i::wasm::max_module_size(),
+                                       &thrower, &is_shared);
   if (thrower.error()) {
     resolver->OnInstantiationFailed(thrower.Reify());
     return;
