[PATCH] wifi: mt76: mt7921: fix memory leak when skb_linearize fails in mcu rx event

[Prashant Rahul]

The ownership of sk_buff skb is passed to mt7921_queue_rx_skb, each
path inside it under the switch case handles cleaning of skb and it
is true for mt7921_mcu_rx_event as well.

mt7921_mcu_rx_event, on a success path, either queues skb via
mt76_mcu_rx_event or cleans it immediately inside
mt7921_mcu_uni_rx_unsolicited_event.

However inside mt7921_mcu_rx_event, if skb_linearize fails, the function
returns immediately and never bothers cleaning skb which leaks skb.

Since skb is fully owned at this point, it is safe to call
dev_kfree_skb which fixes the leak.

Granted, the skb_linearize failure is rare as it can only fail under
heavy memory usage, but at the same time, leaking memory under heavy
memory usage can worsen the OOM condition.

Signed-off-by: Prashant Rahul <prashantrahul23@xxxxxxxxx>
---
 drivers/net/wireless/mediatek/mt76/mt7921/mcu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c
index 25b9437250f7b..fb18d3b4e27ba 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mcu.c
@@ -351,8 +351,10 @@ void mt7921_mcu_rx_event(struct mt792x_dev *dev, struct sk_buff *skb)
 {
 	struct mt76_connac2_mcu_rxd *rxd;
 
-	if (skb_linearize(skb))
+	if (skb_linearize(skb)) {
+		dev_kfree_skb(skb);
 		return;
+	}
 
 	rxd = (struct mt76_connac2_mcu_rxd *)skb->data;
 

---
base-commit: b8809969e1d7a591e0f49dd464a5d04b3cf02ab1
change-id: 20260716-mt7921-mem-leak-a38cbc1d8132

Best regards,
-- 
Prashant Rahul <prashantrahul23@xxxxxxxxx>