CVE-2026-90326
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In the Linux kernel, blk-cgroup has a race between policy activation and blkg destruction. When switching an IO scheduler, blkcg_activate_policy() may race with concurrent blkcg deletion, leading to use-after-free and memory leak issues. Additionally, blkg_free_workfn() frees pd before removing the blkg from q->blkg_list, allowing allocation of a new pd for a blkg being destroyed.
Risk Assessment
May lead to use-after-free and memory leaks in the kernel, potentially enabling privilege escalation or system hang.
Recommendation
Update the Linux kernel to a version containing the fix that extends blkcg_mutex coverage to serialize blkcg_activate_policy() rollback and blkg destruction.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix race between policy activation and blkg destruction When switching an IO scheduler on a block device, blkcg_activate_policy() allocates blkg_policy_data (pd) for all blkgs attached to the queue. However, blkcg_activate_policy() may race with concurrent blkcg deletion, leading to use-after-free and memory leak issues. The use-after-free occurs in the following race: T1 (blkcg_activate_policy): - Successfully allocates pd for blkg1 (loop0->queue, blkcgA) - Fails to allocate pd for blkg2 (loop0->queue, blkcgB) - Enters the enomem rollback path to release blkg1 resources T2 (blkcg deletion): - blkcgA is deleted concurrently - blkg1 is freed via blkg_free_workfn() - blkg1->pd is freed T1 (continued): - Rollback path accesses blkg1->pd->online after pd is freed - Triggers use-after-free In addition, blkg_free_workfn() frees pd before removing the blkg from q->blkg_list. This allows blkcg_activate_policy() to allocate a new pd for a blkg that is being destroyed, leaving the newly allocated pd unreachable when the blkg is finally freed. Fix these races by extending blkcg_mutex coverage to serialize blkcg_activate_policy() rollback and blkg destruction, ensuring pd lifecycle is synchronized with blkg list visibility.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS