[PATCH 3.16 164/178] sr9700: use skb_cow_head() to deal with cloned skbs

[Ben Hutchings]

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>

commit d532c1082f68176363ed766d09bf187616e282fe upstream.

We need to ensure there is enough headroom to push extra header,
but we also need to check if we are allowed to change headers.

skb_cow_head() is the proper helper to deal with this.

Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: James Hughes <james.hughes@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/usb/sr9700.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -456,14 +456,9 @@ static struct sk_buff *sr9700_tx_fixup(s
 
 	len = skb->len;
 
-	if (skb_headroom(skb) < SR_TX_OVERHEAD) {
-		struct sk_buff *skb2;
-
-		skb2 = skb_copy_expand(skb, SR_TX_OVERHEAD, 0, flags);
+	if (skb_cow_head(skb, SR_TX_OVERHEAD)) {
 		dev_kfree_skb_any(skb);
-		skb = skb2;
-		if (!skb)
-			return NULL;
+		return NULL;
 	}
 
 	__skb_push(skb, SR_TX_OVERHEAD);