CVE-2024-42102

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again"

Patch series "mm: Avoid possible overflows in dirty throttling".

Dirty throttling logic assumes dirty limits in page units fit into

32-bits. This patch series makes sure this is true (see patch 2/2 for

more details).

This patch (of 2):

This reverts commit 9319b647902cbd5cc884ac08a8a6d54ce111fc78.

The commit is broken in several ways. Firstly, the removed (u64) cast

from the multiplication will introduce a multiplication overflow on 32-bit

archs if wb_thresh * bg_thresh >= 1<<32 (which is actually common - the

default settings with 4GB of RAM will trigger this). Secondly, the

div64_u64() is unnecessarily expensive on 32-bit archs. We have

div64_ul() in case we want to be safe & cheap. Thirdly, if dirty

thresholds are larger than 1<<32 pages, then dirty balancing is going to

blow up in many other spectacular ways anyway so trying t

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References