netfilter: xtables: fix mangle tables

In POST_ROUTING hook, calling dev_net(in) is going to oops.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/ipv4/netfilter/iptable_mangle.c

@@ -87,7 +87,9 @@ iptable_mangle_hook(unsigned int hook,
 {
 	if (hook == NF_INET_LOCAL_OUT)
 		return ipt_local_hook(hook, skb, in, out, okfn);
-
+	if (hook == NF_INET_POST_ROUTING)
+		return ipt_do_table(skb, hook, in, out,
+				    dev_net(out)->ipv4.iptable_mangle);
 	/* PREROUTING/INPUT/FORWARD: */
 	return ipt_do_table(skb, hook, in, out,
 			    dev_net(in)->ipv4.iptable_mangle);

net/ipv6/netfilter/ip6table_mangle.c

@@ -81,7 +81,9 @@ ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
 {
 	if (hook == NF_INET_LOCAL_OUT)
 		return ip6t_local_out_hook(hook, skb, out, okfn);
-
+	if (hook == NF_INET_POST_ROUTING)
+		return ip6t_do_table(skb, hook, in, out,
+				     dev_net(out)->ipv6.ip6table_mangle);
 	/* INPUT/FORWARD */
 	return ip6t_do_table(skb, hook, in, out,
 			     dev_net(in)->ipv6.ip6table_mangle);