CVE-2024-49854: block, bfq: fix uaf for accessing waker_bfqq after splitting

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-10-21 · updated 2026-08-04
Weakness: CWE-416

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.

Affected products

Linux kernel: from 5.10.227 before 5.15.168; from 5.16 before 6.1.113; from 6.2 before 6.6.54; from 6.7 before 6.10.13; from 6.11 before 6.11.2 — fixed in 5.15.168, 6.1.113, 6.10.13, 6.11.2, 6.6.54

How to fix

Upgrade to a fixed version: Linux kernel 5.15.168, 6.1.113, 6.10.13, 6.11.2. Check the vendor advisory for mitigations.

References

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