net/sched: fix use-after-free in taprio_dev_notifier

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

net/sched: fix use-after-free in taprio_dev_notifier

Since taprio’s taprio_dev_notifier() isn’t protected by an

RCU read-side critical section, a race with advance_sched()

can lead to a use-after-free.

Adding rcu_read_lock() inside taprio_dev_notifier() prevents this.