---
id: "CVE-2026-98864"
kind: "vulnerability"
aliases: ["CVE-2026-98864"]
title: "Linux kernel: sched_ext race can drop task dispatches after reenqueue"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "linux-kernel", "sched-ext"]
not_affected_if: ["default-config"]
published_at: "2026-10-18T16:17:40+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:12:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98864", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel: sched_ext race can drop task dispatches after reenqueue

In the Linux kernel's sched_ext scheduler, a task can be reenqueued while its dispatch is still in progress, and the dispatcher's final state write then overwrites the queued state. The sources describe a scheduling correctness bug where later dispatches of the task are dropped; they do not describe code execution or data access.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Apply the upstream kernel fix that makes reenqueue wait for SCX_OPSS_DISPATCHING to clear, referenced in the NVD entry for CVE-2026-98864
- unknown

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98864

## From the sources

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

sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task

ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics") moved the final
ops_state store in scx_dispatch_enqueue() after the DSQ unlock so that the
custody update and ops.dequeue() precede it. A task can thus be found on a
DSQ while still SCX_OPSS_DISPATCHING.

The dequeue and core-sched pick paths wait for the state to clear in
ops_dequeue() but the reenqueue paths don't. A reenqueue in that window runs
ops.enqueue() and sets SCX_OPSS_QUEUED before the dispatch has completed.
The dispatcher's final store then overwrites it with SCX_OPSS_NONE and
finish_dispatch() drops every later dispatch of the task.

Wait for SCX_OPSS_DISPATCHING to clear before dequeueing a task for
reenqueue, the same way ops_dequeue() does.

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