[PATCH v2] wifi: ath9k: Fix potential array-index-out-of-bounds read in ath9k_htc_txstatus()

[Minsuk Kang <linuxlovemin@yonsei.ac.kr>]

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

Signed-off-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
---
v1->v2:
  Use WARN_ON_ONCE() instead of WARN_ON()

 drivers/net/wireless/ath/ath9k/htc_drv_txrx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
index 800177021baf..efcaeccb055a 100644
--- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
+++ b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
@@ -652,9 +652,10 @@ void ath9k_htc_txstatus(struct ath9k_htc_priv *priv, void *wmi_event)
 	struct ath9k_htc_tx_event *tx_pend;
 	int i;
 
-	for (i = 0; i < txs->cnt; i++) {
-		WARN_ON(txs->cnt > HTC_MAX_TX_STATUS);
+	if (WARN_ON_ONCE(txs->cnt > HTC_MAX_TX_STATUS))
+		return;
 
+	for (i = 0; i < txs->cnt; i++) {
 		__txs = &txs->txstatus[i];
 
 		skb = ath9k_htc_tx_get_packet(priv, __txs);
-- 
2.25.1