---
id: CVE-2026-93253
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sched/isolation: Defer freeing of cpumask memblock memory to initcall

  When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock:
  warn when freeing reserved …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sched/isolation: Defer freeing of cpumask memblock memory to initcall

  When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock:
  warn when freeing reserved …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 27c3a5967f054ab666704cb28f2aeb18ca07cab7 <
    811fdac2d1bdf0b0d3fda262aac288ddd13a1422
  - >-
    Linux >= 27c3a5967f054ab666704cb28f2aeb18ca07cab7 <
    2b58c749b8c5244e259a0230bc57b10b010dc545
  - Linux 7.0
published: '2026-09-24'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T16:17:21.640'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93253'
references:
  - url: 'https://git.kernel.org/stable/c/2b58c749b8c5244e259a0230bc57b10b010dc545'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/811fdac2d1bdf0b0d3fda262aac288ddd13a1422'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-24T16:47:15.832Z'
---

## Overview

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

sched/isolation: Defer freeing of cpumask memblock memory to initcall

When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock:
warn when freeing reserved memory before memory map is initialized"),
the following warning was hit when there was a "nohz_full" kernel boot
parameter.

  Cannot free reserved memory because of deferred initialization of the memory map
  WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swapper/0/0
    :
  Call Trace:
   <TASK>
   memblock_phys_free+0xcb/0x100
   housekeeping_init+0x14c/0x170
   start_kernel+0x207/0x450
   x86_64_start_reservations+0x24/0x30
   x86_64_start_kernel+0xda/0xe0
   common_startup_64+0x13e/0x141
   </TASK>

IOW, we shouldn't free memblock allocated memory so early
in the boot process when memory map isn't fully initialized in
deferred_init_memmap().

Fix it by saving the housekeeping cpumask memblock memory to be
freed into a llist free list in housekeeping_init() and add a new
housekeeping_late_init() helper to defer the actual freeing of memblock
memory to when initcall's are being processed. The cpumask memblock
memory is treated as a llist_node with the size of a "long" type which
is also smallest cpumask size that can be allocated.

The non-atomic version of the llist APIs are used as there is no
contention.

This commit depends on the presence of commit 7c2eee9c1367 ("memblock:
don't touch memblock arrays when memblock_free() is called late")
to prevent a KASAN UAF bug report [1].

 [1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.com/

## Remediation

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