netfilter: nf_conntrack: use safer way to lock all buckets

When we need to lock all buckets in the connection hashtable we'd attempt to
lock 1024 spinlocks, which is way more preemption levels than supported by
the kernel. Furthermore, this behavior was hidden by checking if lockdep is
enabled, and if it was - use only 8 buckets(!).

Fix this by using a global lock and synchronize all buckets on it when we
need to lock them all. This is pretty heavyweight, but is only done when we
need to resize the hashtable, and that doesn't happen often enough (or at all).

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 35 insertions, 19 deletions

diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
index 788ef58a66b9..62e17d1319ff 100644
--- a/include/net/netfilter/nf_conntrack_core.h
+++ b/include/net/netfilter/nf_conntrack_core.h
@@ -79,12 +79,10 @@ print_tuple(struct seq_file *s, const struct nf_conntrack_tuple *tuple,
             const struct nf_conntrack_l3proto *l3proto,
             const struct nf_conntrack_l4proto *proto);
 
-#ifdef CONFIG_LOCKDEP
-# define CONNTRACK_LOCKS 8
-#else
-# define CONNTRACK_LOCKS 1024
-#endif
+#define CONNTRACK_LOCKS 1024
+
 extern spinlock_t nf_conntrack_locks[CONNTRACK_LOCKS];
+void nf_conntrack_lock(spinlock_t *lock);
 
 extern spinlock_t nf_conntrack_expect_lock;
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3cb3cb831591..58882de06bd7 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -66,6 +66,21 @@ EXPORT_SYMBOL_GPL(nf_conntrack_locks);
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock);
 EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock);
 
+static __read_mostly spinlock_t nf_conntrack_locks_all_lock;
+static __read_mostly bool nf_conntrack_locks_all;
+
+void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
+{
+	spin_lock(lock);
+	while (unlikely(nf_conntrack_locks_all)) {
+		spin_unlock(lock);
+		spin_lock(&nf_conntrack_locks_all_lock);
+		spin_unlock(&nf_conntrack_locks_all_lock);
+		spin_lock(lock);
+	}
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_lock);
+
 static void nf_conntrack_double_unlock(unsigned int h1, unsigned int h2)
 {
 	h1 %= CONNTRACK_LOCKS;
@@ -82,12 +97,12 @@ static bool nf_conntrack_double_lock(struct net *net, unsigned int h1,
 	h1 %= CONNTRACK_LOCKS;
 	h2 %= CONNTRACK_LOCKS;
 	if (h1 <= h2) {
-		spin_lock(&nf_conntrack_locks[h1]);
+		nf_conntrack_lock(&nf_conntrack_locks[h1]);
 		if (h1 != h2)
 			spin_lock_nested(&nf_conntrack_locks[h2],
 					 SINGLE_DEPTH_NESTING);
 	} else {
-		spin_lock(&nf_conntrack_locks[h2]);
+		nf_conntrack_lock(&nf_conntrack_locks[h2]);
 		spin_lock_nested(&nf_conntrack_locks[h1],
 				 SINGLE_DEPTH_NESTING);
 	}
@@ -102,16 +117,19 @@ static void nf_conntrack_all_lock(void)
 {
 	int i;
 
-	for (i = 0; i < CONNTRACK_LOCKS; i++)
-		spin_lock_nested(&nf_conntrack_locks[i], i);
+	spin_lock(&nf_conntrack_locks_all_lock);
+	nf_conntrack_locks_all = true;
+
+	for (i = 0; i < CONNTRACK_LOCKS; i++) {
+		spin_lock(&nf_conntrack_locks[i]);
+		spin_unlock(&nf_conntrack_locks[i]);
+	}
 }
 
 static void nf_conntrack_all_unlock(void)
 {
-	int i;
-
-	for (i = 0; i < CONNTRACK_LOCKS; i++)
-		spin_unlock(&nf_conntrack_locks[i]);
+	nf_conntrack_locks_all = false;
+	spin_unlock(&nf_conntrack_locks_all_lock);
 }
 
 unsigned int nf_conntrack_htable_size __read_mostly;
@@ -757,7 +775,7 @@ restart:
 	hash = hash_bucket(_hash, net);
 	for (; i < net->ct.htable_size; i++) {
 		lockp = &nf_conntrack_locks[hash % CONNTRACK_LOCKS];
-		spin_lock(lockp);
+		nf_conntrack_lock(lockp);
 		if (read_seqcount_retry(&net->ct.generation, sequence)) {
 			spin_unlock(lockp);
 			goto restart;
@@ -1382,7 +1400,7 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data),
 	for (; *bucket < net->ct.htable_size; (*bucket)++) {
 		lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS];
 		local_bh_disable();
-		spin_lock(lockp);
+		nf_conntrack_lock(lockp);
 		if (*bucket < net->ct.htable_size) {
 			hlist_nulls_for_each_entry(h, n, &net->ct.hash[*bucket], hnnode) {
 				if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index bd9d31537905..3b40ec575cd5 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -425,7 +425,7 @@ static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 	}
 	local_bh_disable();
 	for (i = 0; i < net->ct.htable_size; i++) {
-		spin_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+		nf_conntrack_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
 		if (i < net->ct.htable_size) {
 			hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 				unhelp(h, me);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index dbb1bb3edb45..355e8552fd5b 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -840,7 +840,7 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 	for (; cb->args[0] < net->ct.htable_size; cb->args[0]++) {
 restart:
 		lockp = &nf_conntrack_locks[cb->args[0] % CONNTRACK_LOCKS];
-		spin_lock(lockp);
+		nf_conntrack_lock(lockp);
 		if (cb->args[0] >= net->ct.htable_size) {
 			spin_unlock(lockp);
 			goto out;
diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
index 5d010f27ac01..94837d236ab0 100644
--- a/net/netfilter/nfnetlink_cttimeout.c
+++ b/net/netfilter/nfnetlink_cttimeout.c
@@ -307,12 +307,12 @@ static void ctnl_untimeout(struct net *net, struct ctnl_timeout *timeout)
 
 	local_bh_disable();
 	for (i = 0; i < net->ct.htable_size; i++) {
-		spin_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+		nf_conntrack_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
 		if (i < net->ct.htable_size) {
 			hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 				untimeout(h, timeout);
 		}
-		spin_unlock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+		nf_conntrack_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
 	}
 	local_bh_enable();
 }