net: openvswitch: fix nf_connlabels leak in ovs_ct_init

ovs_ct_init() acquires a connlabels reference before initializing the
conntrack limit state. If ovs_ct_limit_init() fails, its error is returned
directly. The pernet core does not invoke the exit callback for the
operation whose initialization failed, so ovs_ct_exit() cannot drop the
reference.

This leaves labels_used elevated when Open vSwitch pernet registration
fails for an existing network namespace. Subsequent conntrack entries in
that namespace may allocate label extensions even though Open vSwitch
failed to register.

Drop the connlabels reference before returning a conntrack limit
initialization error. ovs_ct_limit_init() already releases its partial
state, and the original error remains unchanged.

This issue was found by a static analysis checker and confirmed by
manual source review.

Fixes: 11efd5cb04 ("openvswitch: Support conntrack zone limit")
Cc: stable@vger.kernel.org
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://patch.msgid.link/20260815151729.3757984-1-ruoyuw560@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/openvswitch/conntrack.c

@@ -2001,6 +2001,7 @@ int ovs_ct_init(struct net *net)
 {
 	unsigned int n_bits = sizeof(struct ovs_key_ct_labels) * BITS_PER_BYTE;
 	struct ovs_net *ovs_net = net_generic(net, ovs_net_id);
+	int err = 0;
 
 	if (nf_connlabels_get(net, n_bits - 1)) {
 		ovs_net->xt_label = false;
@@ -2010,10 +2011,11 @@ int ovs_ct_init(struct net *net)
 	}
 
 #if	IS_ENABLED(CONFIG_NETFILTER_CONNCOUNT)
-	return ovs_ct_limit_init(net, ovs_net);
-#else
-	return 0;
+	err = ovs_ct_limit_init(net, ovs_net);
+	if (err && ovs_net->xt_label)
+		nf_connlabels_put(net);
 #endif
+	return err;
 }
 
 void ovs_ct_exit(struct net *net)