[PATCH 5.7 085/376] ath11k: Avoid mgmt tx count underflow

[Greg Kroah-Hartman]

From: Sriram R <srirrama@xxxxxxxxxxxxxx>

[ Upstream commit 800113ff4b1d277c2b66ffc04d4d38f202a0d187 ]

The mgmt tx count reference is incremented/decremented on every mgmt tx and on
tx completion event from firmware.
In case of an unexpected mgmt tx completion event from firmware,
the counter would underflow. Avoid this by decrementing
only when the tx count is greater than 0.

Signed-off-by: Sriram R <srirrama@xxxxxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1585567028-9242-1-git-send-email-srirrama@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/wireless/ath/ath11k/wmi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
index 6fec62846279..73beca6d6b5f 100644
--- a/drivers/net/wireless/ath/ath11k/wmi.c
+++ b/drivers/net/wireless/ath/ath11k/wmi.c
@@ -3740,8 +3740,9 @@ static int wmi_process_mgmt_tx_comp(struct ath11k *ar, u32 desc_id,
 
 	ieee80211_tx_status_irqsafe(ar->hw, msdu);
 
-	WARN_ON_ONCE(atomic_read(&ar->num_pending_mgmt_tx) == 0);
-	atomic_dec(&ar->num_pending_mgmt_tx);
+	/* WARN when we received this event without doing any mgmt tx */
+	if (atomic_dec_if_positive(&ar->num_pending_mgmt_tx) < 0)
+		WARN_ON_ONCE(1);
 
 	return 0;
 }
-- 
2.25.1