CVE-2022-50220
Full vulnerability record from the local CVENow database.
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.
Severity
HIGH
CVSS score
7.8
(v3.1)
Vulnerability status
Analyzed
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-06-18 11:15:52.973000
Last modified
2026-11-05 20:17:27.753000
View original CVE JSON
{
"id": "CVE-2022-50220",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-06-18T11:15:52.973",
"lastModified": "2026-11-05T20:17:27.753",
"vulnStatus": "Analyzed",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusbnet: Fix linkwatch use-after-free on disconnect\n\nusbnet uses the work usbnet_deferred_kevent() to perform tasks which may\nsleep. On disconnect, completion of the work was originally awaited in\n->ndo_stop(). But in 2003, that was moved to ->disconnect() by historic\ncommit \"[PATCH] USB: usbnet, prevent exotic rtnl deadlock\":\n\n https://git.kernel.org/tglx/history/c/0f138bbfd83c\n\nThe change was made because back then, the kernel's workqueue\nimplementation did not allow waiting for a single work. One had to wait\nfor completion of *all* work by calling flush_scheduled_work(), and that\ncould deadlock when waiting for usbnet_deferred_kevent() with rtnl_mutex\nheld in ->ndo_stop().\n\nThe commit solved one problem but created another: It causes a\nuse-after-free in USB Ethernet drivers aqc111.c, asix_devices.c,\nax88179_178a.c, ch9200.c and smsc75xx.c:\n\n* If the drivers receive a link change interrupt immediately before\n disconnect, they raise EVENT_LINK_RESET in their (non-sleepable)\n ->status() callback and schedule usbnet_deferred_kevent().\n* usbnet_deferred_kevent() invokes the driver's ->link_reset() callback,\n which calls netif_carrier_{on,off}().\n* That in turn schedules the work linkwatch_event().\n\nBecause usbnet_deferred_kevent() is awaited after unregister_netdev(),\nnetif_carrier_{on,off}() may operate on an unregistered netdev and\nlinkwatch_event() may run after free_netdev(), causing a use-after-free.\n\nIn 2010, usbnet was changed to only wait for a single instance of\nusbnet_deferred_kevent() instead of *all* work by commit 23f333a2bfaf\n(\"drivers/net: don't use flush_scheduled_work()\").\n\nUnfortunately the commit neglected to move the wait back to\n->ndo_stop(). Rectify that omission at long last."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: usbnet: Se corrige el Use-After-Free de linkwatch al desconectar. usbnet usa la función usbnet_deferred_kevent() para ejecutar tareas que podrían estar en estado de suspensión. Al desconectar, la finalización de la tarea se esperaba originalmente en ->ndo_stop(). Sin embargo, en 2003, esto se trasladó a ->disconnect() mediante el commit histórica \"[PATCH] USB: usbnet, previene el bloqueo rtnl exótico\": https://git.kernel.org/tglx/history/c/0f138bbfd83c. Este cambio se realizó porque, en aquel entonces, la implementación de la cola de trabajo del kernel no permitía esperar una sola tarea. Se debía esperar la finalización de *todas* las tareas llamando a flush_scheduled_work(), lo que podía provocar un bloqueo al esperar usbnet_deferred_kevent() con rtnl_mutex en ->ndo_stop(). El commit resolvió un problema pero creó otro: Provoca un uso después de la liberación en los controladores Ethernet USB aqc111.c, asix_devices.c, ax88179_178a.c, ch9200.c y smsc75xx.c: * Si los controladores reciben una interrupción de cambio de enlace inmediatamente antes de la desconexión, generan EVENT_LINK_RESET en su devolución de llamada ->status() (no inactiva) y programan usbnet_deferred_kevent(). * usbnet_deferred_kevent() invoca la devolución de llamada ->link_reset() del controlador, que llama a netif_carrier_{on,off}(). * Eso a su vez programa el trabajo linkwatch_event(). Dado que usbnet_deferred_kevent() se espera después de unregister_netdev(), netif_carrier_{on,off}() puede operar en un netdev no registrado y linkwatch_event() puede ejecutarse después de free_netdev(), lo que provoca un error de uso después de la liberación. En 2010, se modificó la configuración de usbnet para que solo esperara una instancia de usbnet_deferred_kevent() en lugar de *todo* el trabajo mediante el commit 23f333a2bfaf (\"drivers/net: no usar flush_scheduled_work()\"). Lamentablemente, el commit no retrasó la espera a ->ndo_stop(). Se corrigió esta omisión de una vez."
}
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