[PATCH nf-next] netfilter: conntrack: switch connlabels to atomic_t

[PATCH nf-next] netfilter: conntrack: switch connlabels to atomic_t

[Florian Westphal]

The spinlock is back from the day when connabels did not have
a fixed size and reallocation had to be supported.

Remove it.  This change also allows to call the helpers from
softirq or timers without deadlocks.

Also add WARN()s to catch refcounting imbalances.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 include/net/netfilter/nf_conntrack_labels.h |  2 +-
 include/net/netns/conntrack.h               |  2 +-
 net/netfilter/nf_conntrack_labels.c         | 17 ++++++++---------
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_labels.h b/include/net/netfilter/nf_conntrack_labels.h
index fcb19a4e8f2b..6903f72bcc15 100644
--- a/include/net/netfilter/nf_conntrack_labels.h
+++ b/include/net/netfilter/nf_conntrack_labels.h
@@ -39,7 +39,7 @@ static inline struct nf_conn_labels *nf_ct_labels_ext_add(struct nf_conn *ct)
 #ifdef CONFIG_NF_CONNTRACK_LABELS
 	struct net *net = nf_ct_net(ct);
 
-	if (net->ct.labels_used == 0)
+	if (atomic_read(&net->ct.labels_used) == 0)
 		return NULL;
 
 	return nf_ct_ext_add(ct, NF_CT_EXT_LABELS, GFP_ATOMIC);
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index 1f463b3957c7..bae914815aa3 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -107,7 +107,7 @@ struct netns_ct {
 	struct nf_ct_event_notifier __rcu *nf_conntrack_event_cb;
 	struct nf_ip_net	nf_ct_proto;
 #if defined(CONFIG_NF_CONNTRACK_LABELS)
-	unsigned int		labels_used;
+	atomic_t		labels_used;
 #endif
 };
 #endif
diff --git a/net/netfilter/nf_conntrack_labels.c b/net/netfilter/nf_conntrack_labels.c
index 6e70e137a0a6..6c46aad23313 100644
--- a/net/netfilter/nf_conntrack_labels.c
+++ b/net/netfilter/nf_conntrack_labels.c
@@ -11,8 +11,6 @@
 #include <net/netfilter/nf_conntrack_ecache.h>
 #include <net/netfilter/nf_conntrack_labels.h>
 
-static DEFINE_SPINLOCK(nf_connlabels_lock);
-
 static int replace_u32(u32 *address, u32 mask, u32 new)
 {
 	u32 old, tmp;
@@ -60,23 +58,24 @@ EXPORT_SYMBOL_GPL(nf_connlabels_replace);
 
 int nf_connlabels_get(struct net *net, unsigned int bits)
 {
+	int v;
+
 	if (BIT_WORD(bits) >= NF_CT_LABELS_MAX_SIZE / sizeof(long))
 		return -ERANGE;
 
-	spin_lock(&nf_connlabels_lock);
-	net->ct.labels_used++;
-	spin_unlock(&nf_connlabels_lock);
-
 	BUILD_BUG_ON(NF_CT_LABELS_MAX_SIZE / sizeof(long) >= U8_MAX);
 
+	v = atomic_inc_return_relaxed(&net->ct.labels_used);
+	WARN_ON_ONCE(v <= 0);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(nf_connlabels_get);
 
 void nf_connlabels_put(struct net *net)
 {
-	spin_lock(&nf_connlabels_lock);
-	net->ct.labels_used--;
-	spin_unlock(&nf_connlabels_lock);
+	int v = atomic_dec_return_relaxed(&net->ct.labels_used);
+
+	WARN_ON_ONCE(v < 0);
 }
 EXPORT_SYMBOL_GPL(nf_connlabels_put);
-- 
2.41.0

Re: [PATCH nf-next] netfilter: conntrack: switch connlabels to atomic_t

[Pablo Neira Ayuso]

On Fri, Oct 20, 2023 at 02:38:15PM +0200, Florian Westphal wrote:
> The spinlock is back from the day when connabels did not have
> a fixed size and reallocation had to be supported.
> 
> Remove it.  This change also allows to call the helpers from
> softirq or timers without deadlocks.
> 
> Also add WARN()s to catch refcounting imbalances.

Applied, thanks.