CVE-2026-23437

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

net: shaper: protect late read accesses to the hierarchy

We look up a netdev during prep of Netlink ops (pre- callbacks)

and take a ref to it. Then later in the body of the callback

we take its lock or RCU which are the actual protections.

This is not proper, a conversion from a ref to a locked netdev

must include a liveness check (a check if the netdev hasn't been

unregistered already). Fix the read cases (those under RCU).

Writes needs a separate change to protect from creating the

hierarchy after flush has already run.