Divide By Zero Affecting kernel-cross-headers package, versions <0:5.14.0-427.35.1.el9_4


Severity

Recommended
0.0
medium
0
10

Based on AlmaLinux security rating

    Threat Intelligence

    EPSS
    0.04% (6th percentile)

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  • Snyk ID SNYK-ALMALINUX9-KERNELCROSSHEADERS-8339984
  • published 4 Nov 2024
  • disclosed 11 Sep 2024

How to fix?

Upgrade AlmaLinux:9 kernel-cross-headers to version 0:5.14.0-427.35.1.el9_4 or higher.
This issue was patched in ALSA-2024:6567.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-cross-headers package and not the kernel-cross-headers package as distributed by AlmaLinux. See How to fix? for AlmaLinux:9 relevant fixed versions and status.

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 to fix one possible overflow is just moot.

CVSS Scores

version 3.1
Expand this section

NVD

4.7 medium
  • Attack Vector (AV)
    Local
  • Attack Complexity (AC)
    High
  • Privileges Required (PR)
    Low
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    None
  • Integrity (I)
    None
  • Availability (A)
    High
Expand this section

Red Hat

4.7 medium