| Issue |
151015
|
| Summary |
[lld][WebAssembly] `--stack-first` should be the default for wasm-ld
|
| Labels |
lld
|
| Assignees |
|
| Reporter |
whitequark
|
There are several arguments in favor of doing so:
- Without stack protectors enabled by default, any dynamic stack overflow checks, a default stack size of 64K (the smallest of any platform), and no memory protection, WebAssembly is [uniquely vulnerable](https://arxiv.org/abs/2410.17925) to stack smashing in a way that only the simplest microcontrollers that lack an MPU also are.
- Even ignoring the security aspect, the developer experience of encountering a stack overflow in the wild is [confusing and difficult to recognize even for a professional systems developer](https://github.com/WebAssembly/wasi-sdk/issues/551), tools like Wasmtime's `wmemcheck` do not recognize it, and LLVM's suite of sanitizers isn't available to detect it.
- Using `--stack-first` has [no code size overhead](https://github.com/WebAssembly/wasi-sdk/issues/551#issuecomment-3127799692) for the resulting artifact when otherwise default linker options are used.
- Using `--stack-first` in conjunction with `--compress-relocations` has [well below 1% size overhead](https://github.com/WebAssembly/wasi-sdk/issues/551#issuecomment-3127841325).
- Other languages like Rust and Zig pass this option by default for the same reasons.
Although the [memory control](https://github.com/WebAssembly/memory-control) proposal will mitigate the need for this change, that proposal doesn't negate the need to make `--stack-first` the default now:
- Memory control is a Phase 1 proposal with uncertain design and adoption. We need to solve the problems listed above _yesterday_.
- Without inserting `__stkchk` calls, using guard pages won't be enough to eliminate stack smashing for functions that use VLAs or alloca, so even if memory control was widely available, `--stack-first` has its merit.
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