[PPP] generic: Call skb_cow_head before scribbling over skb

It's rude to write over data that other people are still using.  So call
skb_cow_head before PPP proceeds to modify the skb data.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 9293c82ef2af24a9e85a7fc6f0d26fc215797f1b..7e21342becb2eb00175613622649ec9ff7545c4c 100644 (file)
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -899,17 +899,9 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
        /* Put the 2-byte PPP protocol number on the front,
           making sure there is room for the address and control fields. */
-       if (skb_headroom(skb) < PPP_HDRLEN) {
-               struct sk_buff *ns;
-
-               ns = alloc_skb(skb->len + dev->hard_header_len, GFP_ATOMIC);
-               if (ns == 0)
-                       goto outf;
-               skb_reserve(ns, dev->hard_header_len);
-               skb_copy_bits(skb, 0, skb_put(ns, skb->len), skb->len);
-               kfree_skb(skb);
-               skb = ns;
-       }
+       if (skb_cow_head(skb, PPP_HDRLEN))
+               goto outf;
+
        pp = skb_push(skb, 2);
        proto = npindex_to_proto[npi];
        pp[0] = proto >> 8;