CVE-2022-50220
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-06-18

Last updated on: 2025-11-19

Assigner: kernel.org

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.
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Meta Information
Published
2025-06-18
Last Modified
2025-11-19
Generated
2026-05-07
AI Q&A
2025-06-18
EPSS Evaluated
2026-05-05
NVD
CVE-2022-50220
Affected Vendors & Products
Showing 8 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a use-after-free issue in the Linux kernel's usbnet driver. It occurs because the driver schedules work to handle link status changes, but due to a historical change in how the driver waits for this work to complete during device disconnect, the work may run after the network device has been freed. Specifically, if a link change interrupt happens just before disconnect, the driver schedules deferred work that eventually triggers a use-after-free by operating on an unregistered and freed network device.


How can this vulnerability impact me? :

This vulnerability can cause use-after-free conditions in the Linux kernel's USB Ethernet drivers, potentially leading to kernel crashes or undefined behavior. This could affect system stability and security, possibly allowing attackers to cause denial of service or other unintended effects by triggering link change interrupts at specific times.


What immediate steps should I take to mitigate this vulnerability?

Apply the updated Linux kernel patch that fixes the usbnet use-after-free vulnerability by restoring the wait for usbnet_deferred_kevent() completion in the ->ndo_stop() callback. This patch corrects the handling of deferred work on disconnect to prevent use-after-free conditions in affected USB Ethernet drivers.


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