CVE-2026-90326

A flaw was found in the Linux kernel's blk-cgroup component. A race condition exists between the activation of an I/O scheduler policy and the destruction of a block group (blkg). This can lead to a use-after-free vulnerability, where memory is accessed after it has been deallocated, and memory leak issues. A local attacker could potentially exploit this memory corruption to cause a denial of service.

A race in blk cgroup policy activation can occur when blkcg_activate_policy() rolls back after a partial blkg_policy_data allocation failure while another thread destroys the same blkg. The rollback path may access freed blkg policy data, including the online state, which makes this a use after free candidate rather than a simple resource leak. The same lifetime mismatch can also allocate policy data for a blkg that is already being destroyed, leaving the new allocation unreachable. For the CVSS the PR:L is used in the paranoid interpretation because a delegated local actor or reduced-capability admin may be able to participate in cgroup teardown or block policy changes in some deployments. The issue is not network reachable and requires local control plane activity on block cgroup or IO scheduler state. Impact is at least local denial of service via kernel crash. In the worst case it may allow confidentiality or integrity impact due to use after free and should be reviewed manually.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.