CVE-2022-49501

/// Technical description

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

usbnet: Run unregister_netdev() before unbind() again

Commit 2c9d6c2b871d ("usbnet: run unbind() before unregister_netdev()")

sought to fix a use-after-free on disconnect of USB Ethernet adapters.

It turns out that a different fix is necessary to address the issue:

https://lore.kernel.org/netdev/18b3541e5372bc9b9fc733d422f4e698c089077c.1650177997.git.lukas@wunner.de/

So the commit was not necessary.

The commit made binding and unbinding of USB Ethernet asymmetrical:

Before, usbnet_probe() first invoked the ->bind() callback and then

register_netdev(). usbnet_disconnect() mirrored that by first invoking

unregister_netdev() and then ->unbind().

Since the commit, the order in usbnet_disconnect() is reversed and no

longer mirrors usbnet_probe().

One consequence is that a PHY disconnected (and stopped) in ->unbind()

is afterwards stopped once more by unregister_netdev() as it closes the

netdev before unregistering.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References