asix: Fix small memory leak in ax88772_unbind()

When Ethernet frames span mulitple URBs, the netdev buffer memory
pointed to by the asix_rx_fixup_info structure remains allocated
during the time gap between the 2 executions of asix_rx_fixup_internal().

This means that if ax88772_unbind() is called within this time
gap to free the memory of the parent private data structure then
a memory leak of the part filled netdev buffer memory will occur.

Therefore, create a new function asix_rx_fixup_common_free() to
free the memory of the netdev buffer and add a call to
asix_rx_fixup_common_free() from inside ax88772_unbind().

Consequently when an unbind occurs part way through receiving
an Ethernet frame, the netdev buffer memory that is holding part
of the received Ethernet frame will now be freed.

Signed-off-by: Dean Jenkins <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/usb/asix.h

···
 int asix_rx_fixup_internal(struct usbnet *dev, struct sk_buff *skb,
 			   struct asix_rx_fixup_info *rx);
 int asix_rx_fixup_common(struct usbnet *dev, struct sk_buff *skb);
+void asix_rx_fixup_common_free(struct asix_common_private *dp);
 
 struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 			      gfp_t flags);

drivers/net/usb/asix_common.c

···
 	return asix_rx_fixup_internal(dev, skb, rx);
 }
 
+void asix_rx_fixup_common_free(struct asix_common_private *dp)
+{
+	struct asix_rx_fixup_info *rx;
+
+	if (!dp)
+		return;
+
+	rx = &dp->rx_fixup_info;
+
+	if (rx->ax_skb) {
+		kfree_skb(rx->ax_skb);
+		rx->ax_skb = NULL;
+	}
+}
+
 struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 			      gfp_t flags)
 {

drivers/net/usb/asix_devices.c

···
 
 static void ax88772_unbind(struct usbnet *dev, struct usb_interface *intf)
 {
+	asix_rx_fixup_common_free(dev->driver_priv);
 	kfree(dev->driver_priv);
 }