rtl8xxxu: prevent potential memory leak

Free the skb if usb_submit_urb fails on rx_urb. And free the urb
no matter usb_submit_urb succeeds or not in rtl8xxxu_submit_int_urb.
Signed-off-by: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200906040424.22022-1-chiu@endlessm.com

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c

@@ -5795,7 +5795,6 @@ static int rtl8xxxu_submit_int_urb(struct ieee80211_hw *hw)
 	ret = usb_submit_urb(urb, GFP_KERNEL);
 	if (ret) {
 		usb_unanchor_urb(urb);
-		usb_free_urb(urb);
 		goto error;
 	}
 
@@ -5804,6 +5803,7 @@ static int rtl8xxxu_submit_int_urb(struct ieee80211_hw *hw)
 	rtl8xxxu_write32(priv, REG_USB_HIMR, val32);
 
 error:
+	usb_free_urb(urb);
 	return ret;
 }
 
@@ -6318,6 +6318,7 @@ static int rtl8xxxu_start(struct ieee80211_hw *hw)
 	struct rtl8xxxu_priv *priv = hw->priv;
 	struct rtl8xxxu_rx_urb *rx_urb;
 	struct rtl8xxxu_tx_urb *tx_urb;
+	struct sk_buff *skb;
 	unsigned long flags;
 	int ret, i;
 
@@ -6368,6 +6369,13 @@ static int rtl8xxxu_start(struct ieee80211_hw *hw)
 		rx_urb->hw = hw;
 
 		ret = rtl8xxxu_submit_rx_urb(priv, rx_urb);
+		if (ret) {
+			if (ret != -ENOMEM) {
+				skb = (struct sk_buff *)rx_urb->urb.context;
+				dev_kfree_skb(skb);
+			}
+			rtl8xxxu_queue_rx_urb(priv, rx_urb);
+		}
 	}
 
 	schedule_delayed_work(&priv->ra_watchdog, 2 * HZ);