[IPV4]: route: fix crash ip_route_input

[Patrick McHardy <kaber@trash.net>]

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commit dad61a4af7d23146ce67ec2f069f6ba9b75a578d
Author: Patrick McHardy <kaber@trash.net>
Date:   Wed Feb 6 14:35:11 2008 +0100

    [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 b5921910a1 (Routing cache virtualization).
    
    Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8842ecb..525787b 100644
--- a/net/ipv4/route.c
+++ b/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);