---
id: CVE-2026-89756
title: 'mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()

  migrate_pages_batch() unmaps each folio before moving it, and every
  unmap runs the mmu_notifier …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: vendor
cwe:
  - CWE-821
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    8c6d63d434ebb85c6cf3dac1e70a171b183c6614
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    4757542649af56d894e25e30f57cd497dffad53f
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    4996a7bc01ef35570664854dac2530c604981039
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    5dc0daff0341c6baba19c38f47d299ac831d7e99
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    66734981b4d3c105223a13c827c9c73be18d91ad
  - >-
    Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 <
    efe8f86c0916f0f74eea74ae21a3b37f728c6bad
  - Linux 3.18
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:52:09.900Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89756'
references:
  - url: 'https://git.kernel.org/stable/c/8c6d63d434ebb85c6cf3dac1e70a171b183c6614'
  - url: 'https://git.kernel.org/stable/c/4757542649af56d894e25e30f57cd497dffad53f'
  - url: 'https://git.kernel.org/stable/c/4996a7bc01ef35570664854dac2530c604981039'
  - url: 'https://git.kernel.org/stable/c/5dc0daff0341c6baba19c38f47d299ac831d7e99'
  - url: 'https://git.kernel.org/stable/c/66734981b4d3c105223a13c827c9c73be18d91ad'
  - url: 'https://git.kernel.org/stable/c/efe8f86c0916f0f74eea74ae21a3b37f728c6bad'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89756.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89756'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532146'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89756'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89756'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89756.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00197
epssPercentile: 0.09325
ingestedAt: '2026-09-14T15:23:07.448Z'
---

## Overview

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

mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()

migrate_pages_batch() unmaps each folio before moving it, and every
unmap runs the mmu_notifier invalidate callbacks.  On KVM hosts
try_to_migrate() ends up in kvm_mmu_notifier_invalidate_range_start() ->
tdp_mmu_zap_leafs(), which is expensive, so unmapping a large batch keeps
the CPU busy for a long time.

The loop already calls cond_resched(), but on PREEMPTION kernels that is
a no-op, and involuntary preemption is not a Tasks-RCU quiescent state.

A long batch therefore never reports a quiescent state, and the
migrating task (e.g. kcompactd) becomes a Tasks-RCU holdout, stalling the
Tasks-RCU grace period for minutes, which is common at Meta fleet:

  INFO: rcu_tasks detected stalls on tasks:
  0000000055349ecc: .. nvcsw: 1157401/1157401 holdout: 1 idle_cpu: -1/56 task:kcompactd0      state:R  running task
  Call Trace:
   tdp_mmu_zap_leafs
   tdp_mmu_next_root
   gfn_to_pfn_cache_invalidate_start
   kvm_mmu_notifier_invalidate_range_start
   __mmu_notifier_invalidate_range_start
   try_to_migrate_one
   try_to_migrate
   migrate_pages_batch
   migrate_pages
   compact_zone
   compact_node
   kcompactd
   kthread

Use cond_resched_tasks_rcu_qs() so a quiescent state is reported even
when cond_resched() does nothing.

This has also been discussed at [1]

## Affected

- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < 8c6d63d434ebb85c6cf3dac1e70a171b183c6614`
- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < 4757542649af56d894e25e30f57cd497dffad53f`
- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < 4996a7bc01ef35570664854dac2530c604981039`
- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < 5dc0daff0341c6baba19c38f47d299ac831d7e99`
- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < 66734981b4d3c105223a13c827c9c73be18d91ad`
- `Linux >= 8315f42295d2667a7f942f154b73a86fd7cb2227 < efe8f86c0916f0f74eea74ae21a3b37f728c6bad`
- `Linux 3.18`

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89756.json)