Subject: Re: [PATCH net] netfilter: check duplicate config when initializing in ipt_CLUSTERIP

From: Pablo Neira Ayuso <[email-masked]>
Date: Tue, 20 Dec 2016 01:48:03 +0100

On Thu, Dec 15, 2016 at 12:31:40PM +0800, Xin Long wrote:
> @@ -185,6 +186,17 @@ clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
>  	atomic_set(&c->refcount, 1);
>  	atomic_set(&c->entries, 1);
>  
> +	spin_lock_bh(&cn->lock);
> +	if (__clusterip_config_find(net, ip)) {
> +		spin_unlock_bh(&cn->lock);
> +		kfree(c);
> +
> +		return NULL;
> +	}

This is going to result in ENOMEM error report to userspace on race,
which can be confusing. Time for clusterip_config_init() to return
PTR_ERR()?

> +
> +	list_add_rcu(&c->list, &cn->configs);
> +	spin_unlock_bh(&cn->lock);
> +
>  #ifdef CONFIG_PROC_FS
>  	{
>  		char buffer[16];