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.

Classification

CVE ID: CVE-2024-49854

CVSS Base Severity: HIGH

CVSS Base Score: 7.8

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

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 10.48% (scored less or equal to compared to others)

EPSS Date: 2025-06-02 (when was this score calculated)

Stakeholder-Specific Vulnerability Categorization (SSVC)

SSVC Exploitation: none

SSVC Technical Impact: partial

SSVC Automatable: false

References

https://nvd.nist.gov/vuln/detail/CVE-2024-49854
https://git.kernel.org/stable/c/63a07379fdb6c72450cb05294461c6016b8b7726
https://git.kernel.org/stable/c/de0456460f2abf921e356ed2bd8da87a376680bd
https://git.kernel.org/stable/c/0780451f03bf518bc032a7c584de8f92e2d39d7f
https://git.kernel.org/stable/c/0b8bda0ff17156cd3f60944527c9d8c9f99f1583
https://git.kernel.org/stable/c/cae58d19121a70329cf971359e2518c93fec04fe
https://git.kernel.org/stable/c/1ba0403ac6447f2d63914fb760c44a3b19c44eaf

Timeline