wifi: ath9k: Fix potential array-index-out-of-bounds read in ath9k_htc_txstatus()

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

wifi: ath9k: Fix potential array-index-out-of-bounds read in ath9k_htc_txstatus()

Fix an array-index-out-of-bounds read in ath9k_htc_txstatus(). The bug

occurs when txs->cnt, data from a URB provided by a USB device, is

bigger than the size of the array txs->txstatus, which is

HTC_MAX_TX_STATUS. WARN_ON() already checks it, but there is no bug

handling code after the check. Make the function return if that is the

case.

Found by a modified version of syzkaller.

UBSAN: array-index-out-of-bounds in htc_drv_txrx.c

index 13 is out of range for type '__wmi_event_txstatus [12]'

Call Trace:

ath9k_htc_txstatus

ath9k_wmi_event_tasklet

tasklet_action_common

__do_softirq

irq_exit_rxu

sysvec_apic_timer_interrupt