If an skb to be transmitted is shorter than the minimum Ethernet frame
length, we currently set the DMA descriptor length to the minimum but
do not add zero-padding.  This could result in leaking sensitive
data.  We also pass different lengths to dma_map_single() and
dma_unmap_single().

Use skb_padto() to pad properly, before calling dma_map_single().
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>