[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, 3 insertions, 7 deletions

diff --git a/drivers/net/wireless/ray_cs.c b/drivers/net/wireless/ray_cs.c
index 879eb427607c..a915fe6c6aa5 100644
--- a/drivers/net/wireless/ray_cs.c
+++ b/drivers/net/wireless/ray_cs.c
@@ -924,8 +924,7 @@ static int ray_dev_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/wireless/wavelan_cs.c b/drivers/net/wireless/wavelan_cs.c
index f7724eb2fa7e..561250f73fd3 100644
--- a/drivers/net/wireless/wavelan_cs.c
+++ b/drivers/net/wireless/wavelan_cs.c
@@ -3194,11 +3194,8 @@ wavelan_packet_xmit(struct sk_buff *	skb,
 	 * and we don't have the Ethernet specific requirement of beeing
 	 * able to detect collisions, therefore in theory we don't really
 	 * need to pad. Jean II */
-	if (skb->len < ETH_ZLEN) {
-		skb = skb_padto(skb, ETH_ZLEN);
-		if (skb == NULL)
-			return 0;
-	}
+	if (skb_padto(skb, ETH_ZLEN))
+		return 0;
 
   wv_packet_write(dev, skb->data, skb->len);