In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211_hwsim: avoid NULL skb in stop queue drain
mac80211_hwsim_stop() drops any frames left in data->pending. The loop
currently checks skb_queue_empty() and then dequeues separately.
That split is racy with TX status handling, which can remove a pending
frame under the queue lock. If the last entry is removed after the empty
check, skb_dequeue() returns NULL and the stop path passes that NULL skb
to ieee80211_free_txskb().
Use skb_dequeue() as the loop condition instead. The dequeue result is the
object that stop owns and frees, and a concurrent status completion that
empties the queue simply makes the loop terminate.
