CVE-2021-47517

/// Technical description

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

ethtool: do not perform operations on net devices being unregistered

There is a short period between a net device starts to be unregistered

and when it is actually gone. In that time frame ethtool operations

could still be performed, which might end up in unwanted or undefined

behaviours[1].

Do not allow ethtool operations after a net device starts its

unregistration. This patch targets the netlink part as the ioctl one

isn't affected: the reference to the net device is taken and the

operation is executed within an rtnl lock section and the net device

won't be found after unregister.

[1] For example adding Tx queues after unregister ends up in NULL

pointer exceptions and UaFs, such as:

BUG: KASAN: use-after-free in kobject_get+0x14/0x90

Read of size 1 at addr ffff88801961248c by task ethtool/755

CPU: 0 PID: 755 Comm: ethtool Not tainted 5.15.0-rc6+ #778

Hardware name: QEMU Standard PC

/// 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