---
id: CVE-2026-93181
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  perf/x86/intel/uncore: Fix uncore_box ref/unref ordering

  In uncore_event_cpu_online(), uncore_box_ref() was called before
  uncore_change_context()
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  perf/x86/intel/uncore: Fix uncore_box ref/unref ordering

  In uncore_event_cpu_online(), uncore_box_ref() was called before
  uncore_change_context().  uncore_box_ref() ga…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c74443d92f68f07c03ae242ced554b749e6c6736 <
    64aa1bb4017d598828c6d8cd718f43daf2a83375
  - >-
    Linux >= c74443d92f68f07c03ae242ced554b749e6c6736 <
    174f0582e38abe03b88e15f04bfe58490f88cb19
  - Linux 6.11
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:18:14.027'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93181'
references:
  - url: 'https://git.kernel.org/stable/c/174f0582e38abe03b88e15f04bfe58490f88cb19'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/64aa1bb4017d598828c6d8cd718f43daf2a83375'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.727Z'
epss: 0.00189
epssPercentile: 0.08817
---

## Overview

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

perf/x86/intel/uncore: Fix uncore_box ref/unref ordering

In uncore_event_cpu_online(), uncore_box_ref() was called before
uncore_change_context().  uncore_box_ref() gates on box->cpu >= 0,
but box->cpu is still -1 at that point because uncore_change_context()
has not run yet.  As a result, the box is never initialized on the
first CPU to come online in a die, leaving it permanently
uninitialized in the single-CPU-per-die case.

Thus, box->refcnt is one count below the true value, and in the CPU
offline path, the box will be torn down on the second-to-last CPU.

In uncore_event_cpu_offline(), uncore_box_unref() was called after
uncore_change_context(), so box->cpu is already -1 when the collector
CPU goes offline, which prevents it from tearing down the box.

Fix by swapping the call order in both paths so that
uncore_box_{ref,unref}() runs at the point where box->cpu reflects
the correct context.

Move allocate_boxes() out of uncore_box_ref() to enable this
reordering.

## Remediation

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