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fix: heap-use-after-free in build_backtrace when dbuf OOM frees current_exception #1472

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fix: heap-use-after-free in build_backtrace when dbuf OOM frees current_exception #1472

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32 changes: 32 additions & 0 deletions api-test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -765,6 +765,37 @@ static void new_errors(void)
JS_FreeRuntime(rt);
}

static void backtrace_oom_current_exception(void)
{
static const char setup_code[] =
"globalThis.f = function() { missing; };\n"
"Object.defineProperty(f, 'name', { value: 'x'.repeat(2 * 1024 * 1024) });";
JSMemoryUsage stats;
JSValue ret, exception;
JSRuntime *rt;
JSContext *ctx;

rt = new_runtime();
ctx = JS_NewContext(rt);

ret = eval(ctx, setup_code);
assert(!JS_IsException(ret));
JS_FreeValue(ctx, ret);

JS_ComputeMemoryUsage(rt, &stats);
JS_SetMemoryLimit(rt, (size_t)stats.malloc_size + 128 * 1024);

ret = eval(ctx, "f()");
assert(JS_IsException(ret));
assert(JS_HasException(ctx));
exception = JS_GetException(ctx);
JS_FreeValue(ctx, exception);
JS_SetMemoryLimit(rt, 0);

JS_FreeContext(ctx);
JS_FreeRuntime(rt);
}

static int gop_get_own_property(JSContext *ctx, JSPropertyDescriptor *desc,
JSValueConst obj, JSAtom prop)
{
Expand Down Expand Up @@ -1042,6 +1073,7 @@ int main(void)
promise_hook();
dump_memory_usage();
new_errors();
backtrace_oom_current_exception();
global_object_prototype();
slice_string_tocstring();
immutable_array_buffer();
Expand Down
10 changes: 6 additions & 4 deletions quickjs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7743,7 +7743,7 @@ static void build_backtrace(JSContext *ctx, JSValueConst error_val,
int line_num, int col_num, int backtrace_flags)
{
JSStackFrame *sf, *sf_start;
JSValue stack, prepare, saved_exception;
JSValue stack, prepare, saved_exception, error_obj;
DynBuf dbuf;
const char *func_name_str;
const char *str1;
Expand All @@ -7760,6 +7760,7 @@ static void build_backtrace(JSContext *ctx, JSValueConst error_val,
if (rt->in_build_stack_trace)
return;
rt->in_build_stack_trace = true;
error_obj = JS_DupValue(ctx, error_val);
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@saghul saghul May 16, 2026

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use js_dup.


// Save exception because conversion to double may fail.
saved_exception = JS_GetException(ctx);
Expand Down Expand Up @@ -7905,7 +7906,7 @@ static void build_backtrace(JSContext *ctx, JSValueConst error_val,
JS_FreeValue(ctx, csd[k].func_name);
}
JSValueConst args[] = {
error_val,
error_obj,
stack,
};
JSValue stack2 = JS_Call(ctx, prepare, ctx->error_ctor, countof(args), args);
Expand All @@ -7926,13 +7927,14 @@ static void build_backtrace(JSContext *ctx, JSValueConst error_val,

if (JS_IsUndefined(ctx->error_back_trace))
ctx->error_back_trace = js_dup(stack);
if (has_filter_func || can_add_backtrace(error_val)) {
JS_DefinePropertyValue(ctx, error_val, JS_ATOM_stack, stack,
if (has_filter_func || can_add_backtrace(error_obj)) {
JS_DefinePropertyValue(ctx, error_obj, JS_ATOM_stack, stack,
JS_PROP_WRITABLE | JS_PROP_CONFIGURABLE);
} else {
JS_FreeValue(ctx, stack);
}

JS_FreeValue(ctx, error_obj);
rt->in_build_stack_trace = false;
}

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