---
id: CVE-2026-68421
title: 'sched_ext: Don''t warn on core-sched forced idle in put_prev_task_scx()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()

  put_prev_task_scx() warns when a runnable task drops to a lower sched_class
  without SCX_OPS_ENQ_…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b <
    6267ebee9f2f3e26f4968bf6dc29d350620fa320
  - >-
    Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b <
    2907e9d0f05b506dfd58aec589a23042a56ef36b
  - >-
    Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b <
    e2f188cdbf8312289532c36eb4e9eb1c9544d43a
  - >-
    Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b <
    b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da
  - Linux 6.12
published: '2026-08-10'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:44:06.128Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68421'
references:
  - url: 'https://git.kernel.org/stable/c/6267ebee9f2f3e26f4968bf6dc29d350620fa320'
  - url: 'https://git.kernel.org/stable/c/2907e9d0f05b506dfd58aec589a23042a56ef36b'
  - url: 'https://git.kernel.org/stable/c/e2f188cdbf8312289532c36eb4e9eb1c9544d43a'
  - url: 'https://git.kernel.org/stable/c/b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da'
tags:
  - cve.org
epss: 0.00192
epssPercentile: 0.08372
ingestedAt: '2026-10-21T12:48:53.598Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()

put_prev_task_scx() warns when a runnable task drops to a lower sched_class
without SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have
kept it running. Core scheduling breaks that: a forced-idle SMT sibling
reschedules through the core_pick fast path in pick_next_task(), which skips
pick_task_scx() and thus balance_one(), so a runnable task can drop to idle
with ENQ_LAST unset.

Gate the warning on sched_cpu_cookie_match(): a cookie mismatch means core
scheduling forced the idle, while a match (or core scheduling off) still
catches a genuine missing-ENQ_LAST drop.

## Affected

- `Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b < 6267ebee9f2f3e26f4968bf6dc29d350620fa320`
- `Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b < 2907e9d0f05b506dfd58aec589a23042a56ef36b`
- `Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b < e2f188cdbf8312289532c36eb4e9eb1c9544d43a`
- `Linux >= 7c65ae81ea86a6ed8086e1a5651acd766187f19b < b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da`
- `Linux 6.12`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.