3 files changed, 26 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 082a2fd8d85b..369aeabb94fe 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -729,6 +729,9 @@ static void nf_ct_gc_expired(struct nf_conn *ct)
 	if (!refcount_inc_not_zero(&ct->ct_general.use))
 		return;
 
+	/* load ->status after refcount increase */
+	smp_acquire__after_ctrl_dep();
+
 	if (nf_ct_should_gc(ct))
 		nf_ct_kill(ct);
 
@@ -795,6 +798,9 @@ __nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,
 		 */
 		ct = nf_ct_tuplehash_to_ctrack(h);
 		if (likely(refcount_inc_not_zero(&ct->ct_general.use))) {
+			/* re-check key after refcount */
+			smp_acquire__after_ctrl_dep();
+
 			if (likely(nf_ct_key_equal(h, tuple, zone, net)))
 				goto found;
 
@@ -1387,6 +1393,9 @@ static unsigned int early_drop_list(struct net *net,
 		if (!refcount_inc_not_zero(&tmp->ct_general.use))
 			continue;
 
+		/* load ->ct_net and ->status after refcount increase */
+		smp_acquire__after_ctrl_dep();
+
 		/* kill only if still in same netns -- might have moved due to
 		 * SLAB_TYPESAFE_BY_RCU rules.
 		 *
@@ -1536,6 +1545,9 @@ static void gc_worker(struct work_struct *work)
 			if (!refcount_inc_not_zero(&tmp->ct_general.use))
 				continue;
 
+			/* load ->status after refcount increase */
+			smp_acquire__after_ctrl_dep();
+
 			if (gc_worker_skip_ct(tmp)) {
 				nf_ct_put(tmp);
 				continue;
@@ -1775,6 +1787,16 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
 	if (!exp)
 		__nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
 
+	/* Other CPU might have obtained a pointer to this object before it was
+	 * released.  Because refcount is 0, refcount_inc_not_zero() will fail.
+	 *
+	 * After refcount_set(1) it will succeed; ensure that zeroing of
+	 * ct->status and the correct ct->net pointer are visible; else other
+	 * core might observe CONFIRMED bit which means the entry is valid and
+	 * in the hash table, but its not (anymore).
+	 */
+	smp_wmb();
+
 	/* Now it is going to be associated with an sk_buff, set refcount to 1. */
 	refcount_set(&ct->ct_general.use, 1);
 
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 722af5e309ba..f5905b5201a7 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1203,6 +1203,7 @@ restart:
 					   hnnode) {
 			ct = nf_ct_tuplehash_to_ctrack(h);
 			if (nf_ct_is_expired(ct)) {
+				/* need to defer nf_ct_kill() until lock is released */
 				if (i < ARRAY_SIZE(nf_ct_evict) &&
 				    refcount_inc_not_zero(&ct->ct_general.use))
 					nf_ct_evict[i++] = ct;
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 6ad7bbc90d38..05895878610c 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -306,6 +306,9 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	if (unlikely(!refcount_inc_not_zero(&ct->ct_general.use)))
 		return 0;
 
+	/* load ->status after refcount increase */
+	smp_acquire__after_ctrl_dep();
+
 	if (nf_ct_should_gc(ct)) {
 		nf_ct_kill(ct);
 		goto release;