netfilter: connlabels: change nf_connlabels_get bit arg to 'highest used'

nf_connlabel_set() takes the bit number that we would like to set.
nf_connlabels_get() however took the number of bits that we want to
support.

So e.g. nf_connlabels_get(32) support bits 0 to 31, but not 32.
This changes nf_connlabels_get() to take the highest bit that we want
to set.

Callers then don't have to cope with a potential integer wrap
when using nf_connlabels_get(bit + 1) anymore.

Current callers are fine, this change is only to make folloup
nft ct label set support simpler.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack_labels.h

@@ -53,11 +53,11 @@ int nf_connlabels_replace(struct nf_conn *ct,
 #ifdef CONFIG_NF_CONNTRACK_LABELS
 int nf_conntrack_labels_init(void);
 void nf_conntrack_labels_fini(void);
-int nf_connlabels_get(struct net *net, unsigned int n_bits);
+int nf_connlabels_get(struct net *net, unsigned int bit);
 void nf_connlabels_put(struct net *net);
 #else
 static inline int nf_conntrack_labels_init(void) { return 0; }
 static inline void nf_conntrack_labels_fini(void) {}
-static inline int nf_connlabels_get(struct net *net, unsigned int n_bits) { return 0; }
+static inline int nf_connlabels_get(struct net *net, unsigned int bit) { return 0; }
 static inline void nf_connlabels_put(struct net *net) {}
 #endif

net/netfilter/nf_conntrack_labels.c

@@ -78,15 +78,14 @@ int nf_connlabels_replace(struct nf_conn *ct,
 }
 EXPORT_SYMBOL_GPL(nf_connlabels_replace);
 
-int nf_connlabels_get(struct net *net, unsigned int n_bits)
+int nf_connlabels_get(struct net *net, unsigned int bits)
 {
 	size_t words;
 
-	if (n_bits > (NF_CT_LABELS_MAX_SIZE * BITS_PER_BYTE))
+	words = BIT_WORD(bits) + 1;
+	if (words > NF_CT_LABELS_MAX_SIZE / sizeof(long))
 		return -ERANGE;
 
-	words = BITS_TO_LONGS(n_bits);
-
 	spin_lock(&nf_connlabels_lock);
 	net->ct.labels_used++;
 	if (words > net->ct.label_words)
@@ -115,6 +114,8 @@ static struct nf_ct_ext_type labels_extend __read_mostly = {
 
 int nf_conntrack_labels_init(void)
 {
+	BUILD_BUG_ON(NF_CT_LABELS_MAX_SIZE / sizeof(long) >= U8_MAX);
+
 	spin_lock_init(&nf_connlabels_lock);
 	return nf_ct_extend_register(&labels_extend);
 }

net/netfilter/nft_ct.c

@@ -484,6 +484,8 @@ static struct nft_expr_type nft_ct_type __read_mostly = {
 
 static int __init nft_ct_module_init(void)
 {
+	BUILD_BUG_ON(NF_CT_LABELS_MAX_SIZE > NFT_REG_SIZE);
+
 	return nft_register_expr(&nft_ct_type);
 }
 

net/netfilter/xt_connlabel.c

@@ -65,7 +65,7 @@ static int connlabel_mt_check(const struct xt_mtchk_param *par)
 		return ret;
 	}
 
-	ret = nf_connlabels_get(par->net, info->bit + 1);
+	ret = nf_connlabels_get(par->net, info->bit);
 	if (ret < 0)
 		nf_ct_l3proto_module_put(par->family);
 	return ret;

net/openvswitch/conntrack.c

@@ -1344,7 +1344,7 @@ void 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);
 
-	if (nf_connlabels_get(net, n_bits)) {
+	if (nf_connlabels_get(net, n_bits - 1)) {
 		ovs_net->xt_label = false;
 		OVS_NLERR(true, "Failed to set connlabel length");
 	} else {