1 files changed, 21 insertions, 4 deletions

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 26a668a..cc430f9 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -157,11 +157,22 @@ dsthash_find(const struct xt_hashlimit_htable *ht,
 /* allocate dsthash_ent, initialize dst, put in htable and lock it */
 static struct dsthash_ent *
 dsthash_alloc_init(struct xt_hashlimit_htable *ht,
-		   const struct dsthash_dst *dst)
+		   const struct dsthash_dst *dst, bool *race)
 {
 	struct dsthash_ent *ent;
 
 	spin_lock(&ht->lock);
+
+	/* Two or more packets may race to create the same entry in the
+	 * hashtable, double check if this packet lost race.
+	 */
+	ent = dsthash_find(ht, dst);
+	if (ent != NULL) {
+		spin_unlock(&ht->lock);
+		*race = true;
+		return ent;
+	}
+
 	/* initialize hash with random val at the time we allocate
 	 * the first hashtable entry */
 	if (unlikely(!ht->rnd_initialized)) {
@@ -585,6 +596,7 @@ hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	unsigned long now = jiffies;
 	struct dsthash_ent *dh;
 	struct dsthash_dst dst;
+	bool race = false;
 	u32 cost;
 
 	if (hashlimit_init_dst(hinfo, &dst, skb, par->thoff) < 0)
@@ -593,13 +605,18 @@ hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	rcu_read_lock_bh();
 	dh = dsthash_find(hinfo, &dst);
 	if (dh == NULL) {
-		dh = dsthash_alloc_init(hinfo, &dst);
+		dh = dsthash_alloc_init(hinfo, &dst, &race);
 		if (dh == NULL) {
 			rcu_read_unlock_bh();
 			goto hotdrop;
+		} else if (race) {
+			/* Already got an entry, update expiration timeout */
+			dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
+			rateinfo_recalc(dh, now, hinfo->cfg.mode);
+		} else {
+			dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);
+			rateinfo_init(dh, hinfo);
 		}
-		dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);
-		rateinfo_init(dh, hinfo);
 	} else {
 		/* update expiration timeout */
 		dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);