diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 815956ac5a76..85de2a7b0ede 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -936,10 +936,18 @@ __nf_conntrack_confirm(struct sk_buff *skb)
 	 * REJECT will give spurious warnings here.
 	 */
 
-	/* No external references means no one else could have
-	 * confirmed us.
+	/* Another skb with the same unconfirmed conntrack may
+	 * win the race. This may happen for bridge(br_flood)
+	 * or broadcast/multicast packets do skb_clone with
+	 * unconfirmed conntrack.
 	 */
-	WARN_ON(nf_ct_is_confirmed(ct));
+	if (unlikely(nf_ct_is_confirmed(ct))) {
+		WARN_ON_ONCE(1);
+		nf_conntrack_double_unlock(hash, reply_hash);
+		local_bh_enable();
+		return NF_DROP;
+	}
+
 	pr_debug("Confirming conntrack %p\n", ct);
 	/* We have to check the DYING flag after unlink to prevent
 	 * a race against nf_ct_get_next_corpse() possibly called from