In the Linux kernel, the following vulnerability has been resolved:
blk-cgroup: dropping parent refcount after pd_free_fn() is done
Some cgroup policies will access parent pd through child pd even after pd_offline_fn() is done. If pd_free_fn() for parent is called before child, then UAF can be triggered. Hence it's better to guarantee the order of pd_free_fn().
Currently refcount of parent blkg is dropped in __blkg_release(), which is before pd_free_fn() is called in blkg_free_work_fn() while blkg_free_work_fn() is called asynchronously.
This patch make sure pd_free_fn() called from removing cgroup is ordered by delaying dropping parent refcount after calling pd_free_fn() for child.
BTW, pd_free_fn() will also be called from blkcg_deactivate_policy() from deleting device, and following patches will guarantee the order.
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade kernelUpgrade kernel-headersUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-libbpfUpgrade kernel-tools-develUpgrade kernel-libbpf-develUpgrade python3-perfUpgrade kernel-libbpf-staticUpgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade bpftoolUpgrade kernel-livepatch-6.1.19-30.43Upgrade kernel-develUpgrade perf-debuginfoUpgrade perfUpgrade bpftool-debuginfoUpgrade python3-perf-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-tools | Feb 20, 2026 | Dec 24, 2025 |
| Debian | — | Upgrade linux | Jul 27, 2026 | Jul 27, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Dec 24, 2025 |
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