CVE-2024-49854: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix uaf for accessing waker_bfqq after splitting After commit 42c306ed7233 ("block, bfq: don't break merge chain in bfq_split_bfqq()"), if the current procress is the last holder of bfqq, the bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and then access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq may in the merge chain of bfqq, hence just recored waker_bfqq is still not safe. Fix the problem by adding a helper bfq_waker_bfqq() to check if bfqq->waker_bfqq is in the merge chain, and current procress is the only holder.

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CVSS v3.1 Score

7.8

HIGH

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

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.10.227 — 5.15.168
linux	linux_kernel	5.16 — 6.1.113
linux	linux_kernel	6.2 — 6.6.54
linux	linux_kernel	6.7 — 6.10.13
linux	linux_kernel	6.11 — 6.11.2

References

Advisories & Patches

https://git.kernel.org/stable/c/0780451f03bf518bc032a7c584de8f92e2d39d7f https://git.kernel.org/stable/c/0b8bda0ff17156cd3f60944527c9d8c9f99f1583 https://git.kernel.org/stable/c/1ba0403ac6447f2d63914fb760c44a3b19c44eaf https://git.kernel.org/stable/c/63a07379fdb6c72450cb05294461c6016b8b7726 https://git.kernel.org/stable/c/cae58d19121a70329cf971359e2518c93fec04fe https://git.kernel.org/stable/c/de0456460f2abf921e356ed2bd8da87a376680bd

Other References

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

Frequently Asked Questions

What is CVE-2024-49854? +

In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix uaf for accessing waker_bfqq after splitting After commit 42c306ed7233 ("block, bfq: don't break merge chain in bfq_split_bfqq()"), if the current procress is the last holder of bfqq, the bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and then access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq may in the merge chain of bfqq, hence just recored waker_bfqq is still not safe. Fix the problem by adding a helper bfq_waker_bfqq() to check if bfqq->waker_bfqq is in the merge chain, and current procress is the only holder. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2024-49854? +

CVE-2024-49854 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-49854? +

CVE-2024-49854 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-2024-49854? +

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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