---
id: CVE-2025-22070
title: 'fs/9p: fix NULL pointer dereference on mkdir'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fs/9p: fix NULL pointer dereference on mkdir

  When a 9p tree was mounted with option 'posixacl', parent directory had a
  default ACL set for its subdirectories, e.g.:

   …
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'
cvssSource: adp
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    d5031a71a2d0e76d3eb02b52b21c17c881919d53
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    b17edabd917142d9ecd058f7c6ee9da5e32af1dd
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    8522051c58d68146b93e8a5ba9987e83b3d64e7b
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    2139dea5c53e3bb63ac49a6901c85e525a80ee8a
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    6517b395cb1e43fbf3962dd93e6fb4a5e5ab100e
  - >-
    Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 <
    3f61ac7c65bdb26accb52f9db66313597e759821
  - Linux 6.0
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-10-01T16:15:56.459715Z'
published: '2025-04-16'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:21:12.512Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-22070'
references:
  - url: 'https://git.kernel.org/stable/c/d5031a71a2d0e76d3eb02b52b21c17c881919d53'
  - url: 'https://git.kernel.org/stable/c/b17edabd917142d9ecd058f7c6ee9da5e32af1dd'
  - url: 'https://git.kernel.org/stable/c/8522051c58d68146b93e8a5ba9987e83b3d64e7b'
  - url: 'https://git.kernel.org/stable/c/2139dea5c53e3bb63ac49a6901c85e525a80ee8a'
  - url: 'https://git.kernel.org/stable/c/6517b395cb1e43fbf3962dd93e6fb4a5e5ab100e'
  - url: 'https://git.kernel.org/stable/c/3f61ac7c65bdb26accb52f9db66313597e759821'
tags:
  - cve.org
epss: 0.0024
epssPercentile: 0.15141
ingestedAt: '2026-10-21T12:48:53.714Z'
---

## Overview

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

fs/9p: fix NULL pointer dereference on mkdir

When a 9p tree was mounted with option 'posixacl', parent directory had a
default ACL set for its subdirectories, e.g.:

  setfacl -m default:group:simpsons:rwx parentdir

then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in
function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL
(since dafbe689736) even though the subsequent v9fs_set_create_acl() call
expects a valid non-NULL 'fid' pointer:

  [   37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000
  ...
  [   37.322338] Call Trace:
  [   37.323043]  <TASK>
  [   37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434)
  [   37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714)
  [   37.325532] ? search_module_extables (kernel/module/main.c:3733)
  [   37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet
  [   37.328006] ? search_bpf_extables (kernel/bpf/core.c:804)
  [   37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538)
  [   37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574)
  [   37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet
  [   37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p
  [   37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p
  [   37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p
  [   37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p
  [   37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p
  [   37.338590] vfs_mkdir (fs/namei.c:4313)
  [   37.339535] do_mkdirat (fs/namei.c:4336)
  [   37.340465] __x64_sys_mkdir (fs/namei.c:4354)
  [   37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
  [   37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Fix this by simply swapping the sequence of these two calls in
v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before
v9fs_fid_add().

## Affected

- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < d5031a71a2d0e76d3eb02b52b21c17c881919d53`
- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < b17edabd917142d9ecd058f7c6ee9da5e32af1dd`
- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < 8522051c58d68146b93e8a5ba9987e83b3d64e7b`
- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < 2139dea5c53e3bb63ac49a6901c85e525a80ee8a`
- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < 6517b395cb1e43fbf3962dd93e6fb4a5e5ab100e`
- `Linux >= dafbe689736f62c696ac64809b17bdc752cfbe76 < 3f61ac7c65bdb26accb52f9db66313597e759821`
- `Linux 6.0`

## Remediation

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