netfilter: nf_ct_helper: unlink helper again when hash resize happen

From: Liping Zhang <liping.zhang@spreadtrum.com>

Similar to ctnl_untimeout, when hash resize happened, we should try
to do unhelp from the 0# bucket again.
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_helper.c

@@ -409,6 +409,8 @@ void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 	struct nf_conntrack_expect *exp;
 	const struct hlist_node *next;
 	const struct hlist_nulls_node *nn;
+	unsigned int last_hsize;
+	spinlock_t *lock;
 	struct net *net;
 	unsigned int i;
 
@@ -446,13 +448,18 @@ void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 	rtnl_unlock();
 
 	local_bh_disable();
-	for (i = 0; i < nf_conntrack_htable_size; i++) {
-		nf_conntrack_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
-		if (i < nf_conntrack_htable_size) {
-			hlist_nulls_for_each_entry(h, nn, &nf_conntrack_hash[i], hnnode)
-				unhelp(h, me);
+restart:
+	last_hsize = nf_conntrack_htable_size;
+	for (i = 0; i < last_hsize; i++) {
+		lock = &nf_conntrack_locks[i % CONNTRACK_LOCKS];
+		nf_conntrack_lock(lock);
+		if (last_hsize != nf_conntrack_htable_size) {
+			spin_unlock(lock);
+			goto restart;
 		}
-		spin_unlock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+		hlist_nulls_for_each_entry(h, nn, &nf_conntrack_hash[i], hnnode)
+			unhelp(h, me);
+		spin_unlock(lock);
 	}
 	local_bh_enable();
 }