Hi Prakash,
I recommend taking a look at Laverdet's approach used in Node.js:
https://github.com/laverdet/isolated-vm
-J
On Monday, June 4, 2018 at 3:35:58 AM UTC-7, Prakash Bailkeri wrote:
>
> Hello V8-Experts,
>
> I am working on a project where I need to run untrusted user provided
> javascript. I am worried about faulty user script bringing down the entire
> application by hogging memory. So, idea is to implement budgeting of heap
> memory for each javascript.
>
> I looked at different projects that tried to solve the process exit due
> to OOM error. Few ideas that collected are
> 1. Running separate thread and RequestInterrupt. In interrupt
> routine, using GetHeapStatistics to check heap usage.
> https://github.com/phpv8/v8js/blob/php7/v8js_timer.cc#L36:13
> 2. Using AddGCEpilogueCallback and GetHeapStatistics
>
> https://github.com/discourse/mini_racer/blob/master/ext/mini_racer_extension/mini_racer_extension.cc#L194:13
>
> I am worried about the overhead and performance impact of these approaches.
>
> Recently, following commit introduced "AddNearHeapLimitCallback".
>
> Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=824214
> Commit:
> https://chromium.googlesource.com/v8/v8/+/84a80e103b090f35334fe2d168ece17489395417
>
> I tried using this API in my sample program to detect OOM and dispose the
> isolate executing faulty script. [Please see below for the sample program]
> My experiment *detected* the OOM error and terminated the faulty script.
>
> I have few questions regarding this API:
> 1. Are there any caveats in using this API? How reliably it detects the
> OOM condition? Are there scenarios in which it will fail to detect the OOM?
> 2. In the sample code below, in function, "MyNearHeapLimitCallback": I am
> terminating the execution and returning the new heap limit by adding 5MB.
> If I return the initial_heap_limit as is (i.e. without adding 5 MB), the
> faulty script will make my application crash with OOM. Why?
> 3. When the AddNearHeapLimitCallback is being called, I assume that the
> javascript execution is paused. Is this a correct understanding?
>
> Thanks, Prakash
>
>
> ==== Sample program ==
>
> size_t MyNearHeapLimitCallback(void* data, size_t current_heap_limit,
> size_t initial_heap_limit) {
> v8::Isolate *isolate = (v8::Isolate *)data;
> isolate->TerminateExecution();
> return initial_heap_limit + 5 * 1024 * 1024;
> }
>
>
> int main(int argc, char* argv[]) {
> v8::V8::InitializeICUDefaultLocation(argv[0]);
> v8::V8::InitializeExternalStartupData(argv[0]);
> std::unique_ptr<v8::Platform> platform =
> v8::platform::NewDefaultPlatform();
> v8::V8::InitializePlatform(platform.get());
> v8::V8::Initialize();
> while(true) {
> v8::Isolate::CreateParams create_params;
> create_params.array_buffer_allocator =
> v8::ArrayBuffer::Allocator::NewDefaultAllocator();
> v8::ResourceConstraints constraints;
> constraints.set_max_old_space_size(10);
> create_params.constraints = constraints;
> v8::Isolate* isolate = v8::Isolate::New(create_params);
> isolate->AddNearHeapLimitCallback(MyNearHeapLimitCallback, isolate);
> {
> v8::Isolate::Scope isolate_scope(isolate);
> v8::HandleScope handle_scope(isolate);
> v8::Local<v8::Context> context = v8::Context::New(isolate);
> v8::Context::Scope context_scope(context);
> v8::Local<v8::String> source =
> v8::String::NewFromUtf8(isolate, "a = []; for (;;) {
> a.push('hello'); }",
> v8::NewStringType::kNormal)
> .ToLocalChecked();
>
> v8::Local<v8::Script> script = v8::Script::Compile(context,
> source).ToLocalChecked();
>
> v8::TryCatch try_catch(isolate);
> v8::MaybeLocal<v8::Value> result;
> result = script->Run(context);
> if (try_catch.HasCaught() && try_catch.HasTerminated()) {
> isolate->CancelTerminateExecution();
> }
> }
> delete create_params.array_buffer_allocator;
> isolate->Dispose();
> }
> v8::V8::Dispose();
> v8::V8::ShutdownPlatform();
> return 0;
> }
>
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