[ Upstream commit 835acf5d ]

l2tp_xmit_skb() can leak one skb if skb_cow_head() returns an error.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>