---
id: CVE-2025-68372
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nbd: defer config put in recv_work

  There is one uaf issue in recv_work when running NBD_CLEAR_SOCK and
  NBD_CMD_RECONFIGURE:
    nbd_genl_connect     // conf_ref=2 (conne…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nbd: defer config put in recv_work

  There is one uaf issue in recv_work when running NBD_CLEAR_SOCK and
  NBD_CMD_RECONFIGURE:
    nbd_genl_connect     // conf_ref=2 (conne…
severity: none
published: '2025-12-24'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T11:10:00.203'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-68372'
references:
  - url: 'https://git.kernel.org/stable/c/198aa230a6f8c1f6af7ed26b29180749c3e79e4d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1ba2ced2bbdf7e64a30c3e88c70ea8bc208d1509'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3692884bd6187d89d41eef81e5a9724519fd01c1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/443a1721806b6ff6303b5229e9811d68172d622f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6b69593f72e1bfba6ca47ca8d9b619341fded7d6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/742012f6bf29553fdc460bf646a58df3a7b43d01'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9517b82d8d422d426a988b213fdd45c6b417b86d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d3ba312675911ff9e3fefefd551751e153a9f0a9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00198
epssPercentile: 0.0883
ingestedAt: '2026-10-13T11:23:51.154Z'
---

## Overview

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

nbd: defer config put in recv_work

There is one uaf issue in recv_work when running NBD_CLEAR_SOCK and
NBD_CMD_RECONFIGURE:
  nbd_genl_connect     // conf_ref=2 (connect and recv_work A)
  nbd_open	       // conf_ref=3
  recv_work A done     // conf_ref=2
  NBD_CLEAR_SOCK       // conf_ref=1
  nbd_genl_reconfigure // conf_ref=2 (trigger recv_work B)
  close nbd	       // conf_ref=1
  recv_work B
    config_put         // conf_ref=0
    atomic_dec(&config->recv_threads); -> UAF

Or only running NBD_CLEAR_SOCK:
  nbd_genl_connect   // conf_ref=2
  nbd_open 	     // conf_ref=3
  NBD_CLEAR_SOCK     // conf_ref=2
  close nbd
    nbd_release
      config_put     // conf_ref=1
  recv_work
    config_put 	     // conf_ref=0
    atomic_dec(&config->recv_threads); -> UAF

Commit 87aac3a80af5 ("nbd: call nbd_config_put() before notifying the
waiter") moved nbd_config_put() to run before waking up the waiter in
recv_work, in order to ensure that nbd_start_device_ioctl() would not
be woken up while nbd->task_recv was still uncleared.

However, in nbd_start_device_ioctl(), after being woken up it explicitly
calls flush_workqueue() to make sure all current works are finished.
Therefore, there is no need to move the config put ahead of the wakeup.

Move nbd_config_put() to the end of recv_work, so that the reference is
held for the whole lifetime of the worker thread. This makes sure the
config cannot be freed while recv_work is still running, even if clear
+ reconfigure interleave.

In addition, we don't need to worry about recv_work dropping the last
nbd_put (which causes deadlock):

path A (netlink with NBD_CFLAG_DESTROY_ON_DISCONNECT):
  connect  // nbd_refs=1 (trigger recv_work)
  open nbd // nbd_refs=2
  NBD_CLEAR_SOCK
  close nbd
    nbd_release
      nbd_disconnect_and_put
        flush_workqueue // recv_work done
      nbd_config_put
        nbd_put // nbd_refs=1
      nbd_put // nbd_refs=0
        queue_work

path B (netlink without NBD_CFLAG_DESTROY_ON_DISCONNECT):
  connect  // nbd_refs=2 (trigger recv_work)
  open nbd // nbd_refs=3
  NBD_CLEAR_SOCK // conf_refs=2
  close nbd
    nbd_release
      nbd_config_put // conf_refs=1
      nbd_put // nbd_refs=2
  recv_work done // conf_refs=0, nbd_refs=1
  rmmod // nbd_refs=0

Depends-on: e2daec488c57 ("nbd: Fix hungtask when nbd_config_put")

## Remediation

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