[PATCH net 3/6] sr9700: use skb_cow_head() to deal with cloned skbs

[Eric Dumazet]

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 <eduma...@google.com>
Cc: James Hughes <james.hug...@raspberrypi.org>
---
 drivers/net/usb/sr9700.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
index 
4a1e9c489f1f455388ffee289d65e1d6b36cba42..aadfe1d1c37ee67e2a7d17c759db12dad248c41d
 100644
--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -456,14 +456,9 @@ static struct sk_buff *sr9700_tx_fixup(struct usbnet *dev, 
struct sk_buff *skb,
 
        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);
-- 
2.12.2.816.g2cccc81164-goog