skge: fix broken driver

The patch 136d8f3 broke the skge driver.
Note this part of the patch:
+               if (skge_rx_setup(skge, e, nskb, skge->rx_buf_size) < 0) {
+                       dev_kfree_skb(nskb);
+                       goto resubmit;
+               }
+
                pci_unmap_single(skge->hw->pdev,
                                 dma_unmap_addr(e, mapaddr),
                                 dma_unmap_len(e, maplen),
                                 PCI_DMA_FROMDEVICE);
                skb = e->skb;
                prefetch(skb->data);
-               skge_rx_setup(skge, e, nskb, skge->rx_buf_size);

The function skge_rx_setup modifies e->skb to point to the new skb. Thus,
after this change, the new buffer, not the old, is returned to the
networking stack.

This bug is present in kernels 3.11, 3.11.1 and 3.12-rc1. The patch should
be queued for 3.11-stable.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: Vasiliy Glazov <vascom2@gmail.com>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/skge.c

@@ -3092,6 +3092,9 @@ static struct sk_buff *skge_rx_get(struct net_device *dev,
 		if (!nskb)
 			goto resubmit;
 
+		skb = e->skb;
+		prefetch(skb->data);
+
 		if (skge_rx_setup(skge, e, nskb, skge->rx_buf_size) < 0) {
 			dev_kfree_skb(nskb);
 			goto resubmit;
@@ -3101,8 +3104,6 @@ static struct sk_buff *skge_rx_get(struct net_device *dev,
 				 dma_unmap_addr(e, mapaddr),
 				 dma_unmap_len(e, maplen),
 				 PCI_DMA_FROMDEVICE);
-		skb = e->skb;
-		prefetch(skb->data);
 	}
 
 	skb_put(skb, len);