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>

1 files changed, 6 insertions, 6 deletions

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 831aa33d078a..5f19fb0f025d 100644
--- 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) {