Fix(wasi): enable configurable stack overflow protection

.github/workflows/ci.yml

@@ -469,6 +469,8 @@ jobs:
           wasmtime run build/qjs -qd
           echo "console.log('hello wasi!');" > t.js
           wasmtime run --dir . build/qjs t.js
+          wasmtime run --dir . build/qjs --stack-size 64K tests/wasi-stack-limit.js
+          wasmtime run --dir . build/qjs tests/wasi-stack-limit.js
       - name: build wasi reactor
         run: |
           cmake -B build -DQJS_BUILD_WERROR=ON -DCMAKE_TOOLCHAIN_FILE=/opt/wasi-sdk/share/cmake/wasi-sdk.cmake -DQJS_WASI_REACTOR=ON

CMakeLists.txt

@@ -173,6 +173,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
         _WASI_EMULATED_SIGNAL
     )
     add_link_options(
+        -Wl,-z,stack-size=2097152
         -lwasi-emulated-process-clocks
         -lwasi-emulated-signal
     )

quickjs.c

@@ -2368,9 +2368,6 @@ JSRuntime *JS_NewRuntime2(const JSMallocFunctions *mf, void *opaque)
     rt->js_class_id_alloc = JS_CLASS_INIT_COUNT;
 
     rt->stack_size = JS_DEFAULT_STACK_SIZE;
-#ifdef __wasi__
-    rt->stack_size = 0;
-#endif
 
     JS_UpdateStackTop(rt);
 
@@ -3122,15 +3119,11 @@ JSRuntime *JS_GetRuntime(JSContext *ctx)
 
 static void update_stack_limit(JSRuntime *rt)
 {
-#if defined(__wasi__)
-    rt->stack_limit = 0; /* no limit */
-#else
-    if (rt->stack_size == 0) {
+    if (rt->stack_size == 0 || rt->stack_top < rt->stack_size) {
         rt->stack_limit = 0; /* no limit */
     } else {
         rt->stack_limit = rt->stack_top - rt->stack_size;
     }
-#endif
 }
 
 void JS_SetMaxStackSize(JSRuntime *rt, size_t stack_size)

tests/wasi-stack-limit.js

@@ -0,0 +1,22 @@
+let overflow;
+
+// Use a large interpreter frame so QuickJS's linear-memory stack guard trips
+// before Wasmtime's independent WebAssembly call stack is exhausted.
+const args = Array(1024).fill("0").join(",");
+const recurse = Function(
+    `return function recurse() { recurse(${args}); }`
+)();
+
+try {
+    recurse();
+} catch (error) {
+    overflow = error;
+}
+
+if (!(overflow instanceof Error) ||
+    !/stack/i.test(overflow.message)) {
+    throw new Error(`expected a stack overflow, got ${overflow}`);
+}
+
+if (Function("return 20 + 22")() !== 42)
+    throw new Error("runtime is unusable after stack overflow");