---
id: CVE-2026-90190
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  null_blk: use DEFINE_MUTEX for the file-scope mutex

  In null_init(), mutex_init(&lock) currently happens after
  configfs_register_subsystem(), which exposes the nullb su…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  null_blk: use DEFINE_MUTEX for the file-scope mutex

  In null_init(), mutex_init(&lock) currently happens after
  configfs_register_subsystem(), which exposes the nullb su…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    f9f4ca45c770b7eec83fea6c9b727b26e691b513
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    349903f7ee72f7ac5b7a98840d701b2082d140a3
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    0a8c2f7b95981913ac370683e34db4906970c210
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    c7dea90c9b4ef1dfbd2e4df36de180c76fd7c33c
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    234117949da3b3f9705a21b66094f9f30bbe681d
  - >-
    Linux >= 49c3b9266a718dbd73c42e004288b4bb2ea0ac0b <
    017dac7670909eaea3eb36e6b3b5a8be9ce0a14d
  - Linux 5.19
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:17:13.670'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90190'
references:
  - url: 'https://git.kernel.org/stable/c/017dac7670909eaea3eb36e6b3b5a8be9ce0a14d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/0a8c2f7b95981913ac370683e34db4906970c210'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/234117949da3b3f9705a21b66094f9f30bbe681d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/349903f7ee72f7ac5b7a98840d701b2082d140a3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c7dea90c9b4ef1dfbd2e4df36de180c76fd7c33c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f9f4ca45c770b7eec83fea6c9b727b26e691b513'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.864Z'
epss: 0.00205
epssPercentile: 0.10899
---

## Overview

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

null_blk: use DEFINE_MUTEX for the file-scope mutex

In null_init(), mutex_init(&lock) currently happens after
configfs_register_subsystem(), which exposes the nullb subsystem to
userspace. A racing mkdir() into /sys/kernel/config/nullb/ can reach
null_find_dev_by_name() -> mutex_lock(&lock) before the mutex is
initialized, trigger warning:

[  123.137788] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
[  123.137796] WARNING: kernel/locking/mutex.c:159 at mutex_lock+0x171/0x1c0, CPU#13: mkdir/1301
[  123.140090] Modules linked in: null_blk(+) nft_fib_inet nft_fib_ipv4
......
[  123.154926] Call Trace:
[  123.155172]  <TASK>
[  123.155419]  ? __pfx_mutex_lock+0x10/0x10
[  123.156181]  ? __pfx__raw_spin_lock+0x10/0x10
[  123.156571]  nullb_group_make_group+0x20/0x100 [null_blk]
[  123.157011]  configfs_mkdir+0x47b/0xc70
[  123.157337]  ? __pfx_configfs_mkdir+0x10/0x10
[  123.157719]  ? may_create_dentry+0x242/0x2e0
[  123.158061]  vfs_mkdir+0x2a9/0x6c0
[  123.158352]  filename_mkdirat+0x3dc/0x500
[  123.158710]  ? __pfx_filename_mkdirat+0x10/0x10
[  123.159070]  ? strncpy_from_user+0x3a/0x1d0
[  123.159413]  __x64_sys_mkdir+0x6b/0x90
[  123.159760]  do_syscall_64+0xea/0x600

Replace the runtime mutex_init(&lock) with a static DEFINE_MUTEX(lock)
declaration to fix this issue.

## Remediation

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