WebKit JIT ByteCodeParser::handleIntrinsicCall Type Confusion

WebKit JIT has type confusion bugs in ByteCodeParser::handleIntrinsicCall.

MD5 | 872dd200e93696ff2906aeea62a0ced9

WebKit: JIT: Type confusion bugs in ByteCodeParser::handleIntrinsicCall 


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.

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++) {

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

Found by: lokihardt

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