net: ipv6: fix use after free of struct seg6_pernet_data

sdata->tun_src should be freed before sdata is freed
because sdata->tun_src is allocated after sdata allocation.
So, kfree(sdata) and kfree(rcu_dereference_raw(sdata->tun_src)) are
changed code order.

Fixes: f04ed7d2 ("net: ipv6: check return value of rhashtable_init")
Signed-off-by: MichelleJin <shjy180909@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/seg6.c

@@ -375,8 +375,8 @@ static int __net_init seg6_net_init(struct net *net)
 
 #ifdef CONFIG_IPV6_SEG6_HMAC
 	if (seg6_hmac_net_init(net)) {
-		kfree(sdata);
 		kfree(rcu_dereference_raw(sdata->tun_src));
+		kfree(sdata);
 		return -ENOMEM;
 	};
 #endif