[IPV4] nl_fib_lookup: Initialise res.r before fib_res_put(&res)

When CONFIG_IP_MULTIPLE_TABLES is enabled, the code in nl_fib_lookup()
needs to initialize the res.r field before fib_res_put(&res) - unlike
fib_lookup(), a direct call to ->tb_lookup does not set this field.
Signed-off-by: NSergey Vlasov <vsu@altlinux.ru>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/fib_frontend.c

@@ -777,6 +777,10 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb )
 							    .tos = frn->fl_tos,
 							    .scope = frn->fl_scope } } };
 
+#ifdef CONFIG_IP_MULTIPLE_TABLES
+	res.r = NULL;
+#endif
+
 	frn->err = -ENOENT;
 	if (tb) {
 		local_bh_disable();