CVE-2024-42245: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: Revert "sched/fair: Make sure to try to detach at least one movable task" This reverts commit b0defa7ae03ecf91b8bfd10ede430cff12fcbd06. b0defa7ae03ec changed the load balancing logic to ignore env.max_loop if all tasks examined to that point were pinned. The goal of the patch was to make it more likely to be able to detach a task buried in a long list of pinned tasks. However, this has the unfortunate side effect of creating an O(n) iteration in detach_tasks(), as we now must fully iterate every task on a cpu if all or most are pinned. Since this load balance code is done with rq lock held, and often in softirq context, it is very easy to trigger hard lockups. We observed such hard lockups with a user who affined O(10k) threads to a single cpu. When I discussed this with Vincent he initially suggested that we keep the limit on the number of tasks to detach, but increase the number of tasks we can search. However, after some back and forth on the mailing list, he recommended we instead revert the original patch, as it seems likely no one was actually getting hit by the original issue.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-667 CWE-667

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.1 — 6.1.100
linux	linux_kernel	6.2 — 6.6.41
linux	linux_kernel	6.7 — 6.9.10

References

Advisories & Patches

https://git.kernel.org/stable/c/0fa6dcbfa2e2b97c1e6febbea561badf0931a38b https://git.kernel.org/stable/c/1e116c18e32b035a2d1bd460800072c8bf96bc44 https://git.kernel.org/stable/c/2feab2492deb2f14f9675dd6388e9e2bf669c27a https://git.kernel.org/stable/c/d467194018dd536fe6c65a2fd3aedfcdb1424903

Other References

https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html

Frequently Asked Questions

What is CVE-2024-42245? +

In the Linux kernel, the following vulnerability has been resolved: Revert "sched/fair: Make sure to try to detach at least one movable task" This reverts commit b0defa7ae03ecf91b8bfd10ede430cff12fcbd06. b0defa7ae03ec changed the load balancing logic to ignore env.max_loop if all tasks examined to that point were pinned. The goal of the patch was to make it more likely to be able to detach a task buried in a long list of pinned tasks. However, this has the unfortunate side effect of creating an O(n) iteration in detach_tasks(), as we now must fully iterate every task on a cpu if all or most are pinned. Since this load balance code is done with rq lock held, and often in softirq context, it is very easy to trigger hard lockups. We observed such hard lockups with a user who affined O(10k) threads to a single cpu. When I discussed this with Vincent he initially suggested that we keep the limit on the number of tasks to detach, but increase the number of tasks we can search. However, after some back and forth on the mailing list, he recommended we instead revert the original patch, as it seems likely no one was actually getting hit by the original issue. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2024-42245? +

CVE-2024-42245 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2024-42245? +

CVE-2024-42245 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-42245? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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