[NET]: Avoid allocating skb in skb_pad

First of all it is unnecessary to allocate a new skb in skb_pad since
the existing one is not shared.  More importantly, our hard_start_xmit
interface does not allow a new skb to be allocated since that breaks
requeueing.

This patch uses pskb_expand_head to expand the existing skb and linearize
it if needed.  Actually, someone should sift through every instance of
skb_pad on a non-linear skb as they do not fit the reasons why this was
originally created.

Incidentally, this fixes a minor bug when the skb is cloned (tcpdump,
TCP, etc.).  As it is skb_pad will simply write over a cloned skb.  Because
of the position of the write it is unlikely to cause problems but still
it's best if we don't do it.

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

1 files changed, 2 insertions, 5 deletions

diff --git a/drivers/net/depca.c b/drivers/net/depca.c
index 0941d40f046f..e946c43d3b10 100644
--- a/drivers/net/depca.c
+++ b/drivers/net/depca.c
@@ -938,11 +938,8 @@ static int depca_start_xmit(struct sk_buff *skb, struct net_device *dev)
         if (skb->len < 1)
                 goto out;
 
-        if (skb->len < ETH_ZLEN) {
-                skb = skb_padto(skb, ETH_ZLEN);
-                if (skb == NULL)
-                        goto out;
-        }
+        if (skb_padto(skb, ETH_ZLEN))
+                goto out;
         
         netif_stop_queue(dev);