GetURI causes runtime segfault

[skosch]

Hi there! [I hope I am posting this in the right place; please forgive my ignorance about the Go/WASM ecosystem.]

I am using http-wasm via this Traefik OIDC auth plugin. The plugin calls req.GetURI() in its request handler.

Occasionally, some request crashes the runtime, which I can only fix by restarting Traefik. Unfortunately I haven't been able to isolate a specific example URI. The plugin is written using http-wasm-guest-tinygo, which calls GetURI via GetString. The latter then fails like:

func GetString(fn func(ptr uint32, limit imports.BufLimit) (len uint32)) (result string) {
	size := fn(ReadBufPtr, ReadBufLimit)
	if size == 0 {
		return // If nothing was read, return an empty string.
	} else if size <= ReadBufLimit {
		return string(ReadBuf[:size]) // string will copy the buffer.  <-------  THIS FAILS!
	}
	...
}

I would be grateful for any pointers.

The full stacktrace:

runtime stack:

runtime.throw({0xab3e1, 0x2a})
	/home/runner/sdk/gotip/src/runtime/panic.go:1074 +0x3 fp=0x48c1d8 sp=0x48c1b0 pc=0x14a00003
runtime.sigpanic()
	/home/runner/sdk/gotip/src/runtime/os_wasm.go:26 +0xe fp=0x48c1f8 sp=0x48c1d8 pc=0x121a000e
runtime.mallocgcSmallNoscan(0x22, 0x0, 0x0)
	/home/runner/sdk/gotip/src/runtime/malloc.go:1267 +0x26 fp=0x48c250 sp=0x48c1f8 pc=0x10970026
runtime.mallocgc(0x22, 0x0, 0x0)
	/home/runner/sdk/gotip/src/runtime/malloc.go:1046 +0x17 fp=0x48c288 sp=0x48c250 pc=0x14660017
runtime.slicebytetostring(0x0, 0x86a000, 0x22)
	/home/runner/sdk/gotip/src/runtime/string.go:156 +0xb fp=0x48c2b8 sp=0x48c288 pc=0x1339000b
github.com/http-wasm/http-wasm-guest-tinygo/handler/internal/mem.GetString(0xb8a00)
	/home/runner/go/pkg/mod/github.com/traefik/http-wasm-guest-tinygo@v0.0.0-20240913140402-af96219ffea5/handler/internal/mem/mem.go:44 +0x8 fp=0x48c310 sp=0x48c2b8 pc=0x26c80008
github.com/http-wasm/http-wasm-guest-tinygo/handler.wasmRequest.GetURI(...)
	/home/runner/go/pkg/mod/github.com/traefik/http-wasm-guest-tinygo@v0.0.0-20240913140402-af96219ffea5/handler/request.go:31
github.com/http-wasm/http-wasm-guest-tinygo/handler.(*wasmRequest).GetURI(0x482a60)
	<autogenerated>:1 +0x5 fp=0x48c330 sp=0x48c310 pc=0x26e90005
main.(*TraefikOIDCWasm).handleRequest(0x8607c0, {0x114ef8, 0x482a60}, {0x1142d0, 0x482a60})
	/home/runner/work/traefik-oidc-wasm/traefik-oidc-wasm/main.go:107 +0xd fp=0x48c388 sp=0x48c330 pc=0x274e000d
...