CVE-2026-93220
Received Received - Intake

sched_ext Race Condition in Linux Kernel

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Keep kick_sync waiting on the rq's own CPU kick_sync_wait_bal_cb() assumes it runs on the rq's CPU from the __schedule() tail: the snapshots it compares against live in that CPU's percpu area and the busy-wait runs with the rq lock dropped and IRQs enabled. However, dispatch can now drop the rq lock while the callback sits queued, and rq lock takers in that window (the sched class change paths, the scx task iterator) flush pending balance callbacks on release, running the callback on a foreign CPU. Such a run compares against unrelated snapshots and can deadlock when the executing CPU is itself a wait target. Bail on a foreign CPU and leave the wait state alone. The wait only observes progress that the resched kicks already guarantee and the rq's next wait picks up the stale cpus_to_sync bits.

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Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-25
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-93220
EUVD
EUVD-2026-85949

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

Helpful Resources

Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability where a function called kick_sync_wait_bal_cb() incorrectly assumes it runs on the same CPU as the run queue (rq). The callback compares snapshots from the wrong CPU's memory and can deadlock if the executing CPU is a target for waiting.

Detection Guidance

This vulnerability is specific to the Linux kernel's sched_ext subsystem and requires kernel-level inspection. Detection involves checking kernel logs for related errors or verifying if your kernel version includes the fix. Commands like 'uname -a' can show your kernel version, and 'dmesg | grep sched_ext' may reveal related issues.

Impact Analysis

This could cause system hangs or crashes due to deadlocks in the scheduler, potentially leading to denial of service or instability in systems running affected Linux kernel versions.

Compliance Impact

This vulnerability is a Linux kernel issue related to scheduling and CPU management. It does not directly impact compliance with standards like GDPR or HIPAA, as those focus on data protection and privacy rather than kernel-level scheduling bugs.

Mitigation Strategies

Update your Linux kernel to the latest stable version that includes the fix for this vulnerability. If updating is not immediately possible, avoid using the sched_ext feature until patched. Monitor kernel logs for signs of exploitation or instability.

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