In the Linux kernel, the following vulnerability has been resolved:
wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown
wcn36xx_dxe_deinit() tears down the TX ack timer with timer_delete(),
which only dequeues the timer and does not wait for a callback that is
already executing; the preceding free_irq() calls synchronize the
interrupt handlers only. The callback, wcn36xx_dxe_tx_timer(), can
therefore be running past the teardown and use the wcn freed along
with the ieee80211_hw in wcn36xx_remove(): it takes wcn->dxe_lock,
reads wcn->tx_ack_skb and passes wcn->hw to
ieee80211_tx_status_irqsafe().
Fix this by using timer_shutdown_sync(), which waits for a running
callback and also prevents the timer from being rearmed again. The
timer is set up again by wcn36xx_dxe_init() on the next start, so the
start/stop cycle is unaffected.
This issue was found by an in-house static analysis tool.
