netfilter: ctnetlink: fix possible refcount leak in ctnetlink_create_conntrack()

jira VULN-6817
cve CVE-2023-7192
commit-author Hangyu Hua <hbh25y@gmail.com>
commit ac48939

nf_ct_put() needs to be called to put the refcount got by
nf_conntrack_find_get() to avoid refcount leak when
nf_conntrack_hash_check_insert() fails.

Fixes: 7d367e0 ("netfilter: ctnetlink: fix soft lockup when netlink adds new entries (v2)")
	Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
	Acked-by: Florian Westphal <fw@strlen.de>
	Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit ac48939)
	Signed-off-by: Marcin Wcisło <marcin.wcislo@conclusive.pl>

Author: pvts-mat

net/netfilter/nf_conntrack_netlink.c

@@ -2375,12 +2375,15 @@ ctnetlink_create_conntrack(struct net *net,
 
 	err = nf_conntrack_hash_check_insert(ct);
 	if (err < 0)
-		goto err2;
+		goto err3;
 
 	rcu_read_unlock();
 
 	return ct;
 
+err3:
+	if (ct->master)
+		nf_ct_put(ct->master);
 err2:
 	rcu_read_unlock();
 err1: