[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>

2 files changed, 2 insertions, 4 deletions

diff --git a/drivers/net/pcmcia/fmvj18x_cs.c b/drivers/net/pcmcia/fmvj18x_cs.c
index 09b11761cdfa..ea93b8f18605 100644
--- a/drivers/net/pcmcia/fmvj18x_cs.c
+++ b/drivers/net/pcmcia/fmvj18x_cs.c
@@ -831,8 +831,7 @@ static int fjn_start_xmit(struct sk_buff *skb, struct net_device *dev)
     
     if (length < ETH_ZLEN)
     {
-        skb = skb_padto(skb, ETH_ZLEN);
-        if (skb == NULL)
+        if (skb_padto(skb, ETH_ZLEN))
                 return 0;
         length = ETH_ZLEN;
     }
diff --git a/drivers/net/pcmcia/xirc2ps_cs.c b/drivers/net/pcmcia/xirc2ps_cs.c
index e80d1e3aec68..9bae77ce1314 100644
--- a/drivers/net/pcmcia/xirc2ps_cs.c
+++ b/drivers/net/pcmcia/xirc2ps_cs.c
@@ -1374,8 +1374,7 @@ do_start_xmit(struct sk_buff *skb, struct net_device *dev)
      */
     if (pktlen < ETH_ZLEN)
     {
-        skb = skb_padto(skb, ETH_ZLEN);
-        if (skb == NULL)
+        if (skb_padto(skb, ETH_ZLEN))
                 return 0;
         pktlen = ETH_ZLEN;
     }