Re: [PATCH] net: moxa: fix TX overrun memory leak

From: Jonas Jensen <redacted>
Date: Fri,  5 Jun 2015 15:46:18 +0200

 	desc = priv->tx_desc_base + (TX_REG_DESC_SIZE * tx_head);
 
-	spin_lock_irq(&priv->txlock);
+	if (CIRC_SPACE(tx_head, tx_tail, TX_DESC_NUM) == 0) {
+		priv->stats.tx_dropped++;
+		goto out_unlock;
+	}

You can't do this.

Whatever code creates this condition _must_ stop the TX queue
so that the core netdevice transmit layer does not call your
transmit method.