---
id: CVE-2026-64294
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mm: do file ownership checks with the proper mount idmap

  Ever since idmapped mounts were introduced, inode ownership checks (for
  side-channel protection) in mincore() …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mm: do file ownership checks with the proper mount idmap

  Ever since idmapped mounts were introduced, inode ownership checks (for
  side-channel protection) in mincore() …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.12, < 6.6.145'
  - 'linux_kernel >= 6.7, < 6.12.96'
  - 'linux_kernel >= 6.13, < 6.18.39'
  - 'linux_kernel >= 6.19, < 7.1.4'
  - linux_kernel = 7.2
patched:
  - linux_kernel 7.1.4
published: '2026-07-25'
updated: '2026-08-23'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64294'
references:
  - url: 'https://git.kernel.org/stable/c/04ba248d02d9eaa3d9077b00a6134caa75fa3e90'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5c942ad7df75925ee166e7f0fb36892d8dde376b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7368bec565bac3e536cd43579dbde1e715e6ba61'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/744b23aa430d52f5c8e4dbff7d71496d6643bed2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8344bdf0629457e532797b42d9d2bbf2a2900bbf'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b2f3d94ea310bea9d36d53e9d9b3f45e86c1d893'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e187bc02f8fa4226d62814592cf064ee4557c470'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.0016
epssPercentile: 0.05599
ingestedAt: '2026-08-23T13:48:05.540Z'
---

## Overview

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

mm: do file ownership checks with the proper mount idmap

Ever since idmapped mounts were introduced, inode ownership checks (for
side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done
against the nop_mnt_idmap, which completely ignores the file's mount's
idmap.  This results in odd edgecases like:

1) mount/bind-mount with an idmap userA:userB:1
2) userB runs an owner_or_capable() check on file that is owned by userA
on-disk/in-memory, but owned by userB after idmap translation
3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied

In the case of mincore/madvise MADV_PAGEOUT, this is usually benign,
because file_permission(file, MAY_WRITE) will probably succeed, as it uses
the proper idmap internally, but it does not need to be the case on e.g a
0444 file where even the owner itself doesn't have permissions to write to
it.

Since this is clearly not trivial to get right, introduce a
file_owner_or_capable() that can carry the correct semantics, and switch
the various users in mm to it.

The issue was found by manual code inspection & an off-list discussion
with Jan Kara.

## Affected

- `linux_kernel >= 5.12, < 6.6.145`
- `linux_kernel >= 6.7, < 6.12.96`
- `linux_kernel >= 6.13, < 6.18.39`
- `linux_kernel >= 6.19, < 7.1.4`
- `linux_kernel = 7.2`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`