---
id: CVE-2026-64396
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation

  When a blocking byte-range lock request is deferred in the
  FILE_LOCK_DEFERRED path, ksmbd re…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation

  When a blocking byte-range lock request is deferred in the
  FILE_LOCK_DEFERRED path, ksmbd re…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.15, < 6.1.178'
  - 'linux_kernel >= 6.2, < 6.6.145'
  - 'linux_kernel >= 6.7, < 6.12.96'
  - 'linux_kernel >= 6.13, < 6.18.39'
  - 'linux_kernel >= 6.19, < 7.1.4'
patched:
  - linux_kernel 7.1.4
published: '2026-07-25'
updated: '2026-09-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64396'
references:
  - url: 'https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00435
epssPercentile: 0.37288
ingestedAt: '2026-09-05T13:39:57.690Z'
---

## Overview

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

ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation

When a blocking byte-range lock request is deferred in the
FILE_LOCK_DEFERRED path, ksmbd registers the asynchronous work into
the connection's async_requests list via setup_async_work(). The cancel
callback smb2_remove_blocked_lock() holds a reference to the flock.

If the lock waiter is subsequently woken up but the work state is no
longer KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the
cleanup path calls locks_free_lock(flock) without dequeuing the work from
the async_requests list. Concurrently, smb2_cancel() walks the list
under conn->request_lock and invokes the cancel callback, which then
dereferences the already freed 'flock'. This leads to a slab-use-after-free
inside __wake_up_common.

Fix this by restructuring the cleanup logic after the worker returns
from ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and
release_async_work(work) to the top of the cleanup block. This guarantees
that the async work is completely dequeued and serialized under
conn->request_lock before locks_free_lock(flock) is called, rendering
the flock unreachable for any concurrent smb2_cancel().

## Affected

- `linux_kernel >= 5.15, < 6.1.178`
- `linux_kernel >= 6.2, < 6.6.145`
- `linux_kernel >= 6.7, < 6.12.96`
- `linux_kernel >= 6.13, < 6.18.39`
- `linux_kernel >= 6.19, < 7.1.4`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`