qlcnic: dont assume NET_IP_ALIGN is 2

qlcnic driver allocates rx skbs and gives to hardware too bytes of extra
storage, allowing for corruption of kernel data.

NET_IP_ALIGN being 0 on some platforms (including x86), drivers should
not assume it's 2.

rds_ring->skb_size = rds_ring->dma_size + NET_IP_ALIGN;
...
skb = dev_alloc_skb(rds_ring->skb_size);
skb_reserve(skb, 2);
pci_map_single(pdev, skb->data, rds_ring->dma_size, PCI_DMA_FROMDEVICE);

(and rds_ring->skb_size == rds_ring->dma_size) -> bug


Because of extra alignment (1500 + 32) -> four extra bytes are available
before the struct skb_shared_info, so corruption is not noticed.

Note: this driver could use netdev_alloc_skb_ip_align()
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/qlcnic/qlcnic_init.c

@@ -1316,7 +1316,7 @@ qlcnic_alloc_rx_skb(struct qlcnic_adapter *adapter,
 		return -ENOMEM;
 	}
 
-	skb_reserve(skb, 2);
+	skb_reserve(skb, NET_IP_ALIGN);
 
 	dma = pci_map_single(pdev, skb->data,
 			rds_ring->dma_size, PCI_DMA_FROMDEVICE);