Bug 285505 – Incorrect Index Validation in grow_memory Instruction

• Component: WebAssembly
• Status: RESOLVED INVALID

Created attachment 473821 [details]
program.js

### Description
WebKit does not correctly enforce validation for the `grow_memory` instruction in WebAssembly modules.

### Environment

- OS: Ubuntu 20.04  
- CPU: amd64  
- WebKit Version: 146fa28a329d220785d2972c1d691555141e6406
- Commands:  
```bash
./JSCOnly/Debug/bin/jsc ./program.js
```

### Test Case

program.js



### Current State
```plaintext
./JSCOnly/Debug/bin/jsc ./program.js
Exception: CompileError: WebAssembly.Module doesn't parse at byte 5: reserved byte for grow_memory must be zero, in function at index 0 (evaluating 'new WebAssembly.Module(wasm_code)')
Module@[native code]
```

### Expected Behavior

The WebAssembly module should fail validation and report an error similar to:

- Like gecko-dev:
  ```plaintext
  memory index out of range for memory.grow
  ```
- Like v8:
  ```plaintext
  CompileError: WebAssembly.Module(): Compiling function #0 failed: memory index 2816 exceeds number of declared memories (1) 
  ```

[David Degazio]

It looks like we're still failing at validation time, just reporting a different error message? "must be zero" is more appropriate for WebKit at the moment than "out of range" because we do not yet support the WASM multi-memory proposal (tracked in https://bugs.webkit.org/show_bug.cgi?id=277743).

[Radar WebKit Bug Importer]

<rdar://problem/142489712>

[Yusuke Suzuki]

multi-memory is not implemented.