smsc95xx: Use skb_cow_head to deal with cloned skbs

The driver was failing to check that the SKB wasn't cloned
before adding checksum data.
Replace existing handling to extend/copy the header buffer
with skb_cow_head.

Signed-off-by: James Hughes <james.hughes@raspberrypi.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Woojung Huh <Woojung.Huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 831aa33d078ae7d2dd57fdded5de71d1eb915f99..5f19fb0f025d9449d0ba20958610e0d1f083f032 100644 (file)
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -2001,13 +2001,13 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
        /* We do not advertise SG, so skbs should be already linearized */
        BUG_ON(skb_shinfo(skb)->nr_frags);
 
-       if (skb_headroom(skb) < overhead) {
-               struct sk_buff *skb2 = skb_copy_expand(skb,
-                       overhead, 0, flags);
+       /* Make writable and expand header space by overhead if required */
+       if (skb_cow_head(skb, overhead)) {
+               /* Must deallocate here as returning NULL to indicate error
+                * means the skb won't be deallocated in the caller.
+                */
                dev_kfree_skb_any(skb);
-               skb = skb2;
-               if (!skb)
-                       return NULL;
+               return NULL;
        }
 
        if (csum) {