---
id: CVE-2025-38563
title: 'perf/core: Prevent VMA split of buffer mappings'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  perf/core: Prevent VMA split of buffer mappings

  The perf mmap code is careful about mmap()'ing the user page with the
  ringbuffer and additionally the auxiliary buffer,…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    e4346ffec2c44d6b0be834d59b20632b5bb5729e
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    d52451a9210f2e5a079ba052918c93563518a9ff
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    3bd518cc7ea61076bcd725e36ff0e690754977c0
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    7b84cb58d1f0aa07656802eae24689566e5f5b1b
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    6757a31a8e295ae4f01717a954afda173f25a121
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    e529888b7e8092912dd8789bdfc76685ccd2ff5f
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    ff668930871e0198c7f4e325058b8b7c286787bd
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    65311aad4c808bedad0c05d9bb8b06c47dae73eb
  - >-
    Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff <
    b024d7b56c77191cde544f838debb7f8451cd0d6
  - Linux 4.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:04:01.303949Z'
published: '2025-08-19'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:12:47.209Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38563'
references:
  - url: 'https://git.kernel.org/stable/c/e4346ffec2c44d6b0be834d59b20632b5bb5729e'
  - url: 'https://git.kernel.org/stable/c/d52451a9210f2e5a079ba052918c93563518a9ff'
  - url: 'https://git.kernel.org/stable/c/3bd518cc7ea61076bcd725e36ff0e690754977c0'
  - url: 'https://git.kernel.org/stable/c/7b84cb58d1f0aa07656802eae24689566e5f5b1b'
  - url: 'https://git.kernel.org/stable/c/6757a31a8e295ae4f01717a954afda173f25a121'
  - url: 'https://git.kernel.org/stable/c/e529888b7e8092912dd8789bdfc76685ccd2ff5f'
  - url: 'https://git.kernel.org/stable/c/ff668930871e0198c7f4e325058b8b7c286787bd'
  - url: 'https://git.kernel.org/stable/c/65311aad4c808bedad0c05d9bb8b06c47dae73eb'
  - url: 'https://git.kernel.org/stable/c/b024d7b56c77191cde544f838debb7f8451cd0d6'
  - url: 'https://www.zerodayinitiative.com/advisories/ZDI-25-873/'
tags:
  - cve.org
epss: 0.00403
epssPercentile: 0.34818
zeroDay: true
ingestedAt: '2026-11-05T22:38:31.991Z'
---

## Overview

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

perf/core: Prevent VMA split of buffer mappings

The perf mmap code is careful about mmap()'ing the user page with the
ringbuffer and additionally the auxiliary buffer, when the event supports
it. Once the first mapping is established, subsequent mapping have to use
the same offset and the same size in both cases. The reference counting for
the ringbuffer and the auxiliary buffer depends on this being correct.

Though perf does not prevent that a related mapping is split via mmap(2),
munmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls,
which take reference counts, but then the subsequent perf_mmap_close()
calls are not longer fulfilling the offset and size checks. This leads to
reference count leaks.

As perf already has the requirement for subsequent mappings to match the
initial mapping, the obvious consequence is that VMA splits, caused by
resizing of a mapping or partial unmapping, have to be prevented.

Implement the vm_operations_struct::may_split() callback and return
unconditionally -EINVAL.

That ensures that the mapping offsets and sizes cannot be changed after the
fact. Remapping to a different fixed address with the same size is still
possible as it takes the references for the new mapping and drops those of
the old mapping.

## Affected

- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < e4346ffec2c44d6b0be834d59b20632b5bb5729e`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < d52451a9210f2e5a079ba052918c93563518a9ff`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < 3bd518cc7ea61076bcd725e36ff0e690754977c0`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < 7b84cb58d1f0aa07656802eae24689566e5f5b1b`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < 6757a31a8e295ae4f01717a954afda173f25a121`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < e529888b7e8092912dd8789bdfc76685ccd2ff5f`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < ff668930871e0198c7f4e325058b8b7c286787bd`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < 65311aad4c808bedad0c05d9bb8b06c47dae73eb`
- `Linux >= 45bfb2e50471abbbfd83d40d28c986078b0d24ff < b024d7b56c77191cde544f838debb7f8451cd0d6`
- `Linux 4.1`

## Remediation

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