---
id: CVE-2026-80778
title: 'futex/pi: Reject cross-mm private futex owners'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  futex/pi: Reject cross-mm private futex owners

  A private futex key borrows the waiter's mm without taking an mm_users
  reference. Nevertheless, attach_to_pi_owner() cur…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 80367ad01d93ac781b0e1df246edaf006928002f <
    2b92e5562653b5293529f63b0300837d9dcedbd7
  - >-
    Linux >= 80367ad01d93ac781b0e1df246edaf006928002f <
    f7fb3e07752688842cbe0b85cf0d98c2fbf76b68
  - >-
    Linux >= 80367ad01d93ac781b0e1df246edaf006928002f <
    43b148d796aa338858792d0167cebdc12b8cb4b9
  - >-
    Linux >= 80367ad01d93ac781b0e1df246edaf006928002f <
    59b3732f95dda1fbd2234514d35f4fb6b5bb6d85
  - Linux 6.16
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:43:33.681Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80778'
references:
  - url: 'https://git.kernel.org/stable/c/2b92e5562653b5293529f63b0300837d9dcedbd7'
  - url: 'https://git.kernel.org/stable/c/f7fb3e07752688842cbe0b85cf0d98c2fbf76b68'
  - url: 'https://git.kernel.org/stable/c/43b148d796aa338858792d0167cebdc12b8cb4b9'
  - url: 'https://git.kernel.org/stable/c/59b3732f95dda1fbd2234514d35f4fb6b5bb6d85'
tags:
  - cve.org
epss: 0.00168
epssPercentile: 0.05671
ingestedAt: '2026-10-19T10:20:54.955Z'
---

## Overview

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

futex/pi: Reject cross-mm private futex owners

A private futex key borrows the waiter's mm without taking an mm_users
reference. Nevertheless, attach_to_pi_owner() currently accepts an owner
from a different address space and copies the private key into the owner's
PI state.

When that owner exits, exit_pi_state_list() uses the saved key to find the
hash bucket and acquires a reference to the waiter's private hash. If the
last user of the waiter's mm exits concurrently, futex_hash_free() frees
the hash while the owner still uses its bucket and reference.

Prevent this by validating in attach_to_pi_owner() that, for private
futexes, the owner mm and waiter mm are the same. Perform the check with
the owner's pi_lock held and after validating owner::futex::state to
serialize against a concurrent PI-state exit cleanup.

[ tglx: Amended comment ]

## Affected

- `Linux >= 80367ad01d93ac781b0e1df246edaf006928002f < 2b92e5562653b5293529f63b0300837d9dcedbd7`
- `Linux >= 80367ad01d93ac781b0e1df246edaf006928002f < f7fb3e07752688842cbe0b85cf0d98c2fbf76b68`
- `Linux >= 80367ad01d93ac781b0e1df246edaf006928002f < 43b148d796aa338858792d0167cebdc12b8cb4b9`
- `Linux >= 80367ad01d93ac781b0e1df246edaf006928002f < 59b3732f95dda1fbd2234514d35f4fb6b5bb6d85`
- `Linux 6.16`

## Remediation

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