---
id: CVE-2022-50220
title: 'usbnet: Fix linkwatch use-after-free on disconnect'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  usbnet: Fix linkwatch use-after-free on disconnect

  usbnet uses the work usbnet_deferred_kevent() to perform tasks which may
  sleep.  On disconnect, completion of the wo…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    d2d6b530d89b0a912148018027386aa049f0a309
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    e2a521a7dcc463c5017b4426ca0804e151faeff7
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    7f77dcbc030c2faa6d8e8a594985eeb34018409e
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    8b4588b8b00b299be16a35be67b331d8fdba03f3
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    135199a2edd459d2b123144efcd7f9bcd95128e4
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    635fd8953e4309b54ca6a81bed1d4a87668694f4
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    d49bb8cf9bfaa06aa527eb30f1a52a071da2e32f
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    db3b738ae5f726204876f4303c49cfdf4311403f
  - >-
    Linux >= 23f333a2bfafba80339315b724808982a9de57d9 <
    a69e617e533edddf3fa3123149900f36e0a6dc74
  - Linux 2.6.38
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:07:05.736067Z'
published: '2025-06-18'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:10:29.354Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2022-50220'
references:
  - url: 'https://git.kernel.org/stable/c/d2d6b530d89b0a912148018027386aa049f0a309'
  - url: 'https://git.kernel.org/stable/c/e2a521a7dcc463c5017b4426ca0804e151faeff7'
  - url: 'https://git.kernel.org/stable/c/7f77dcbc030c2faa6d8e8a594985eeb34018409e'
  - url: 'https://git.kernel.org/stable/c/8b4588b8b00b299be16a35be67b331d8fdba03f3'
  - url: 'https://git.kernel.org/stable/c/135199a2edd459d2b123144efcd7f9bcd95128e4'
  - url: 'https://git.kernel.org/stable/c/635fd8953e4309b54ca6a81bed1d4a87668694f4'
  - url: 'https://git.kernel.org/stable/c/d49bb8cf9bfaa06aa527eb30f1a52a071da2e32f'
  - url: 'https://git.kernel.org/stable/c/db3b738ae5f726204876f4303c49cfdf4311403f'
  - url: 'https://git.kernel.org/stable/c/a69e617e533edddf3fa3123149900f36e0a6dc74'
tags:
  - cve.org
epss: 0.00246
epssPercentile: 0.15955
ingestedAt: '2026-11-05T22:38:31.705Z'
---

## Overview

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

usbnet: Fix linkwatch use-after-free on disconnect

usbnet uses the work usbnet_deferred_kevent() to perform tasks which may
sleep.  On disconnect, completion of the work was originally awaited in
->ndo_stop().  But in 2003, that was moved to ->disconnect() by historic
commit "[PATCH] USB: usbnet, prevent exotic rtnl deadlock":

  https://git.kernel.org/tglx/history/c/0f138bbfd83c

The change was made because back then, the kernel's workqueue
implementation did not allow waiting for a single work.  One had to wait
for completion of *all* work by calling flush_scheduled_work(), and that
could deadlock when waiting for usbnet_deferred_kevent() with rtnl_mutex
held in ->ndo_stop().

The commit solved one problem but created another:  It causes a
use-after-free in USB Ethernet drivers aqc111.c, asix_devices.c,
ax88179_178a.c, ch9200.c and smsc75xx.c:

* If the drivers receive a link change interrupt immediately before
  disconnect, they raise EVENT_LINK_RESET in their (non-sleepable)
  ->status() callback and schedule usbnet_deferred_kevent().
* usbnet_deferred_kevent() invokes the driver's ->link_reset() callback,
  which calls netif_carrier_{on,off}().
* That in turn schedules the work linkwatch_event().

Because usbnet_deferred_kevent() is awaited after unregister_netdev(),
netif_carrier_{on,off}() may operate on an unregistered netdev and
linkwatch_event() may run after free_netdev(), causing a use-after-free.

In 2010, usbnet was changed to only wait for a single instance of
usbnet_deferred_kevent() instead of *all* work by commit 23f333a2bfaf
("drivers/net: don't use flush_scheduled_work()").

Unfortunately the commit neglected to move the wait back to
->ndo_stop().  Rectify that omission at long last.

## Affected

- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < d2d6b530d89b0a912148018027386aa049f0a309`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < e2a521a7dcc463c5017b4426ca0804e151faeff7`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < 7f77dcbc030c2faa6d8e8a594985eeb34018409e`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < 8b4588b8b00b299be16a35be67b331d8fdba03f3`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < 135199a2edd459d2b123144efcd7f9bcd95128e4`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < 635fd8953e4309b54ca6a81bed1d4a87668694f4`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < d49bb8cf9bfaa06aa527eb30f1a52a071da2e32f`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < db3b738ae5f726204876f4303c49cfdf4311403f`
- `Linux >= 23f333a2bfafba80339315b724808982a9de57d9 < a69e617e533edddf3fa3123149900f36e0a6dc74`
- `Linux 2.6.38`

## Remediation

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