lan78xx: use skb_cow_head() to deal with cloned skbs

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: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Hughes <james.hughes@raspberrypi.org>
Cc: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 7 deletions

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 9889a70ff4f6..636f48f19d1e 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2607,14 +2607,9 @@ static struct sk_buff *lan78xx_tx_prep(struct lan78xx_net *dev,
 {
         u32 tx_cmd_a, tx_cmd_b;
 
-        if (skb_headroom(skb) < TX_OVERHEAD) {
-                struct sk_buff *skb2;
-
-                skb2 = skb_copy_expand(skb, TX_OVERHEAD, 0, flags);
+        if (skb_cow_head(skb, TX_OVERHEAD)) {
                 dev_kfree_skb_any(skb);
-                skb = skb2;
-                if (!skb)
-                        return NULL;
+                return NULL;
         }
 
         if (lan78xx_linearize(skb) < 0)