netfilter: nf_nat: Fix memleak in nf_nat_init

When register_pernet_subsys() fails, nf_nat_bysource
should be freed just like when nf_ct_extend_register()
fails.

Fixes: 1cd472bf ("netfilter: nf_nat: add nat hook register functions to nf_nat")
Signed-off-by: NDinghao Liu <dinghao.liu@zju.edu.cn>
Acked-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_nat_core.c

@@ -1174,6 +1174,7 @@ static int __init nf_nat_init(void)
 	ret = register_pernet_subsys(&nat_net_ops);
 	if (ret < 0) {
 		nf_ct_extend_unregister(&nat_extend);
+		kvfree(nf_nat_bysource);
 		return ret;
 	}