---
id: CVE-2026-98542
title: >-
  cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on
  subpartitions_cpus conflict
summary: >-
  In the Linux kernel, the following vulnerability has been resolved:


  cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on
  subpartitions_cpus conflict


  When a remote partition is created underneath an existing local partition…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 <
    241e67b60308cdce25bba66616a109759edd1d40
  - >-
    Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 <
    0751ab665cb3dcdac224b002565f2e28461740d5
  - >-
    Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 <
    31c88350b7dd1522792f726f79607f31bb55c50f
  - Linux 6.16
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:18:10.035Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98542'
references:
  - url: 'https://git.kernel.org/stable/c/241e67b60308cdce25bba66616a109759edd1d40'
  - url: 'https://git.kernel.org/stable/c/0751ab665cb3dcdac224b002565f2e28461740d5'
  - url: 'https://git.kernel.org/stable/c/31c88350b7dd1522792f726f79607f31bb55c50f'
tags:
  - cve.org
ingestedAt: '2026-10-18T15:45:12.268Z'
---

## Overview

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

cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict

When a remote partition is created underneath an existing local partition
via a non-partition (PRS_MEMBER) intermediate cgroup, update_prstate() sees
parent->partition_root_state == PRS_MEMBER and calls
remote_partition_enable().

Commit 86888c7bd117 ("cgroup/cpuset: Add warnings to catch inconsistency
in exclusive CPUs") replaced the cpumask_intersects(tmp->new_cpus,
subpartitions_cpus) error check in remote_partition_enable() with
WARN_ON_ONCE(). As a result, remote_partition_enable() emits a warning
and proceeds to enable the remote partition on CPUs that are already
owned by the ancestor local partition in subpartitions_cpus.

This can be reproduced on Linux 7.3.0-rc3 with:

  mkdir -p /tmp/cg1
  mount -t cgroup2 none /tmp/cg1
  echo "+cpuset" > /tmp/cg1/cgroup.subtree_control

  mkdir /tmp/cg1/A
  echo 1 > /tmp/cg1/A/cpuset.cpus
  echo 1 > /tmp/cg1/A/cpuset.cpus.exclusive
  echo root > /tmp/cg1/A/cpuset.cpus.partition
  echo "+cpuset" > /tmp/cg1/A/cgroup.subtree_control

  mkdir /tmp/cg1/A/B
  echo 1 > /tmp/cg1/A/B/cpuset.cpus
  echo 1 > /tmp/cg1/A/B/cpuset.cpus.exclusive
  echo "+cpuset" > /tmp/cg1/A/B/cgroup.subtree_control

  mkdir /tmp/cg1/A/B/D
  echo 1 > /tmp/cg1/A/B/D/cpuset.cpus
  echo 1 > /tmp/cg1/A/B/D/cpuset.cpus.exclusive
  echo root > /tmp/cg1/A/B/D/cpuset.cpus.partition

which triggers:

  WARNING: kernel/cgroup/cpuset.c:1594 at remote_partition_enable+0x1c1/0x300

and leaves both /tmp/cg1/A and /tmp/cg1/A/B/D as active root partitions
claiming exclusive CPU 1.

Fix this by returning PERR_NOCPUS when tmp->new_cpus intersects
subpartitions_cpus in remote_partition_enable(), matching the error code
used by remote_cpus_update() for the same subpartitions_cpus conflict, and
add a regression test case to
tools/testing/selftests/cgroup/test_cpuset_prs.sh.

Tested in QEMU on Linux 7.3.0-rc3 using the reproducer above and
tools/testing/selftests/cgroup/test_cpuset_prs.sh.

## Affected

- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 241e67b60308cdce25bba66616a109759edd1d40`
- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 0751ab665cb3dcdac224b002565f2e28461740d5`
- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 31c88350b7dd1522792f726f79607f31bb55c50f`
- `Linux 6.16`

## Remediation

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