UBUNTU-CVE-2026-89521: High severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: sched/core: Handle picktask() releasing the rq lock Core scheduling's picknexttask() breaks when a ->picktask() implementation can release the rq lock. The selection state derived on entry is only valid while the lock is held continuously. Once a pick can drop the lock, an interleaving selection can invalidate all of it: the single-CPU fast path can commit an uncookied pick although the core went cookied during the release, and forceidle committed by the interleaving selection skews the restarted pass's accounting. Fix it by restarting the whole selection when a pick returns RETRYTASK after releasing the lock: a single restart point above the state derivation replaces the per-loop restart labels, so a retry picks up state committed by interleaving selections and accounts and resets forceidle like a fresh selection would. needsync and fibefore latch across retries. Clock validity can't be re-derived - there is no program-ordered way to tell whether the own and core rq clocks are still updated after the lock was released, as other lockers' pin cycles may or may not have invalidated them. When restarting, clear coreclockupdated so that the sibling loop re-updates the core rq, and update the own rq clock if invalidated.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
Upgrade
ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
Upgrade
ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
Upgrade
ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
Upgrade
ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
Upgrade
ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Compensating control
In Linux kernel sched/core selection, restart the whole selection when pick_task() returns RETRY_TASK after releasing the rq lock. Use a single restart point above state derivation; on restart, clear core_clock_updated, update the own rq clock if invalidated, and preserve need_sync and fi_before across retries.
Event History
Frequently Asked Questions
Which Ubuntu kernel packages are identified as affected?
The listed packages are ubuntu/linux-riscv, ubuntu/linux-realtime, ubuntu/linux-hwe-edge, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-azure-fde, ubuntu/linux-gke, and ubuntu/linux-aws-5.0.
What level of access would an attacker need?
The severity vector indicates local attack access and low privileges are required. No user interaction is required.