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.
Metrics
Affected Vendors & Products
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References
History
Fri, 04 Jul 2025 15:00:00 +0000
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Wed, 18 Jun 2025 11:15:00 +0000
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| Description | 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. | |
| Title | usbnet: Fix linkwatch use-after-free on disconnect | |
| References |
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MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2025-06-18T11:03:55.461Z
Updated: 2025-07-15T15:43:48.595Z
Reserved: 2025-06-18T10:57:27.430Z
Link: CVE-2022-50220
Vulnrichment
No data.
NVD
Status : Awaiting Analysis
Published: 2025-06-18T11:15:52.973
Modified: 2025-06-18T13:47:40.833
Link: CVE-2022-50220
Redhat