[IPV4]: route: fix crash ip_route_input

ip_route_me_harder() may call ip_route_input() with skbs that don't
have skb->dev set for skbs rerouted in LOCAL_OUT and TCP resets
generated by the REJECT target, resulting in a crash when dereferencing
skb->dev->nd_net. Since ip_route_input() has an input device argument,
it seems correct to use that one anyway.

Bug introduced in b592191 (Routing cache virtualization).

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/route.c

@@ -2041,7 +2041,7 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	int iif = dev->ifindex;
 	struct net *net;
 
-	net = skb->dev->nd_net;
+	net = dev->nd_net;
 	tos &= IPTOS_RT_MASK;
 	hash = rt_hash(daddr, saddr, iif);