---
id: CVE-2026-99105
title: >-
  sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its
  CPU's local DSQ
summary: >-
  In the Linux kernel, the following vulnerability has been resolved:


  sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its
  CPU's local DSQ


  With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to

  ops.e…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f <
    ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d
  - >-
    Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f <
    8d891c218016b6145993e082e7f732cb69dd0e29
  - >-
    Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f <
    396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59
  - >-
    Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f <
    7a9df76679633cf26e0fea882a684012c6ec245a
  - Linux 6.12
published: '2026-10-28'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:41:46.163Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99105'
references:
  - url: 'https://git.kernel.org/stable/c/ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d'
  - url: 'https://git.kernel.org/stable/c/8d891c218016b6145993e082e7f732cb69dd0e29'
  - url: 'https://git.kernel.org/stable/c/396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59'
  - url: 'https://git.kernel.org/stable/c/7a9df76679633cf26e0fea882a684012c6ec245a'
tags:
  - cve.org
epss: 0.00168
epssPercentile: 0.0622
ingestedAt: '2026-10-28T11:09:40.456Z'
---

## Overview

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

sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ

With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to
ops.enqueue() instead of being kept running. Exiting tasks without
SCX_OPS_ENQ_EXITING, migration disabled tasks without
SCX_OPS_ENQ_MIGRATION_DISABLED and tasks on an offline rq skip ops.enqueue()
and go straight to the local DSQ. This happens in put_prev_task_scx() after
the pick has settled on idle, so nothing reschedules the CPU, which idles
with the task queued until an unrelated wakeup lands on it or the watchdog
fires.

scx_mitosis, which sets SCX_OPS_ENQ_LAST without SCX_OPS_ENQ_EXITING, hit
this during mass cgroup teardown: exiting tasks stuck in exit_mmap() for
over 40 seconds.

A task put on the local DSQ runs, as anywhere else. If the SCX_ENQ_LAST
enqueue left the task on this CPU's local DSQ, set need_resched on the task
being switched in, as proxy_resched_idle() does. resched_curr() would flag
the task being put instead, and __schedule() clears that right after the
pick.

## Affected

- `Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f < ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d`
- `Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f < 8d891c218016b6145993e082e7f732cb69dd0e29`
- `Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f < 396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59`
- `Linux >= f0e1a0643a59bf1f922fa209cec86a170b784f3f < 7a9df76679633cf26e0fea882a684012c6ec245a`
- `Linux 6.12`

## Remediation

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