---
id: CVE-2025-37878
title: 'perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init

  Move the get_ctx(child_ctx) call and the child_event->ctx assignment to
  occur immediately after the chi…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 7ef5aa081f989ecfecc1df02068a80aebbd3ec31 <
    90dc6c1e3b200812da8d0aa030e1b7fda8226d0e
  - >-
    Linux >= 1209b0b29fd472e7dbd2b06544b019dd9f9b7e51 <
    cb56cd11feabf99e08bc18960700a53322ffcea7
  - >-
    Linux >= c70ca298036c58a88686ff388d3d367e9d21acf0 <
    0ba3a4ab76fd3367b9cb680cad70182c896c795c
  - Linux 315a50c6b1c6ce191f19f3372935d8e2ed9b53a6
  - Linux >= 6.13.12 < 6.14
  - Linux >= 6.12.24 < 6.12.26
  - Linux >= 6.14.3 < 6.14.5
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:44:23.606659Z'
published: '2025-05-09'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:52:06.591Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-37878'
references:
  - url: 'https://git.kernel.org/stable/c/90dc6c1e3b200812da8d0aa030e1b7fda8226d0e'
  - url: 'https://git.kernel.org/stable/c/cb56cd11feabf99e08bc18960700a53322ffcea7'
  - url: 'https://git.kernel.org/stable/c/0ba3a4ab76fd3367b9cb680cad70182c896c795c'
tags:
  - cve.org
epss: 0.00276
epssPercentile: 0.20112
ingestedAt: '2026-11-05T22:38:31.888Z'
---

## Overview

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

perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init

Move the get_ctx(child_ctx) call and the child_event->ctx assignment to
occur immediately after the child event is allocated. Ensure that
child_event->ctx is non-NULL before any subsequent error path within
inherit_event calls free_event(), satisfying the assumptions of the
cleanup code.

Details:

There's no clear Fixes tag, because this bug is a side-effect of
multiple interacting commits over time (up to 15 years old), not
a single regression.

The code initially incremented refcount then assigned context
immediately after the child_event was created. Later, an early
validity check for child_event was added before the
refcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was
added, assuming event->ctx is valid if the pmu_ctx is valid.
The problem is that the WARN_ON_ONCE() could trigger after the initial
check passed but before child_event->ctx was assigned, violating its
precondition. The solution is to assign child_event->ctx right after
its initial validation. This ensures the context exists for any
subsequent checks or cleanup routines, resolving the WARN_ON_ONCE().

To resolve it, defer the refcount update and child_event->ctx assignment
directly after child_event->pmu_ctx is set but before checking if the
parent event is orphaned. The cleanup routine depends on
event->pmu_ctx being non-NULL before it verifies event->ctx is
non-NULL. This also maintains the author's original intent of passing
in child_ctx to find_get_pmu_context before its refcount/assignment.

[ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]

## Affected

- `Linux >= 7ef5aa081f989ecfecc1df02068a80aebbd3ec31 < 90dc6c1e3b200812da8d0aa030e1b7fda8226d0e`
- `Linux >= 1209b0b29fd472e7dbd2b06544b019dd9f9b7e51 < cb56cd11feabf99e08bc18960700a53322ffcea7`
- `Linux >= c70ca298036c58a88686ff388d3d367e9d21acf0 < 0ba3a4ab76fd3367b9cb680cad70182c896c795c`
- `Linux 315a50c6b1c6ce191f19f3372935d8e2ed9b53a6`
- `Linux >= 6.13.12 < 6.14`
- `Linux >= 6.12.24 < 6.12.26`
- `Linux >= 6.14.3 < 6.14.5`

## Remediation

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