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

Bluetooth: hci_event: Fix using rcu_read_(un)lock while iterating

The usage of rcu_read_(un)lock while inside list_for_each_entry_rcu is
not safe since for the most part entries fetched this way shall be
treated as rcu_dereference:

	Note that the value returned by rcu_dereference() is valid
	only within the enclosing RCU read-side critical section [1]_.
	For example, the following is **not** legal::

		rcu_read_lock();
		p = rcu_dereference(head.next);
		rcu_read_unlock();
		x = p->address;	/* BUG!!! */
		rcu_read_lock();
		y = p->data;	/* BUG!!! */
		rcu_read_unlock();

https://git.kernel.org/stable/c/0108132d7d76d884e443d18b4f067cdf2811911b

https://git.kernel.org/stable/c/581dd2dc168fe0ed2a7a5534a724f0d3751c93ae

https://git.kernel.org/stable/c/f9ecc90b5d501b3a5a62d0685d5104f934bb0104