[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, 1 insertions, 2 deletions

diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index 9945cc6b8d90..985afe0e6273 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -2222,8 +2222,7 @@ static int rtl8169_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 len = skb->len;
 
                 if (unlikely(len < ETH_ZLEN)) {
-                        skb = skb_padto(skb, ETH_ZLEN);
-                        if (!skb)
+                        if (skb_padto(skb, ETH_ZLEN))
                                 goto err_update_stats;
                         len = ETH_ZLEN;
                 }