---
id: CVE-2026-99172
title: 'ipc: drop the mqueue mount with kern_unmount() on setup failure'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipc: drop the mqueue mount with kern_unmount() on setup failure

  mq_init_ns() creates the mqueue mount with fc_mount_longterm(), so its
  ->mnt_ns is MNT_NS_INTERNAL. Whe…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= dc55e35f9e810f23dd69cfdc91a3d636023f57a2 <
    c0620b648321fff654173d238d4a85298ea16d05
  - >-
    Linux >= dc55e35f9e810f23dd69cfdc91a3d636023f57a2 <
    f0e48172a59e517e613b73f73cc35f24fd123aeb
  - Linux 5.19
published: '2026-10-28'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T10:35:27.245Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99172'
references:
  - url: 'https://git.kernel.org/stable/c/c0620b648321fff654173d238d4a85298ea16d05'
  - url: 'https://git.kernel.org/stable/c/f0e48172a59e517e613b73f73cc35f24fd123aeb'
tags:
  - cve.org
ingestedAt: '2026-10-28T11:09:40.386Z'
---

## Overview

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

ipc: drop the mqueue mount with kern_unmount() on setup failure

mq_init_ns() creates the mqueue mount with fc_mount_longterm(), so its
->mnt_ns is MNT_NS_INTERNAL. When setting up the mqueue or ipc sysctls
or msg_init_ns() fails afterwards, create_ipc_ns() drops it with a plain
mntput(). With ->mnt_ns set that takes the fast path of
mntput_no_expire(). The count drops to zero and nothing ever kills the
mount, so the mount and the mqueue superblock are leaked.

Commit dc55e35f9e81 ("ipc: Store mqueue sysctls in the ipc namespace")
added the first failure path after mq_init_ns() and never dropped the
mount. Commit 7229d74e5e8c ("ipc: create_ipc_ns: drop mqueue mount on
sysctl setup failure") tried to fix that with a mntput() but that
doesn't help for a long-term mount.

Use kern_unmount(). free_ipc() open-codes the same thing for a namespace
that made it.

## Affected

- `Linux >= dc55e35f9e810f23dd69cfdc91a3d636023f57a2 < c0620b648321fff654173d238d4a85298ea16d05`
- `Linux >= dc55e35f9e810f23dd69cfdc91a3d636023f57a2 < f0e48172a59e517e613b73f73cc35f24fd123aeb`
- `Linux 5.19`

## Remediation

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