netdev - Re: [PATCH net] netfilter: check duplicate config when initializing in ipt

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Message-ID: <20161220004803.GA14656@salvia>
Date:   Tue, 20 Dec 2016 01:48:03 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>,
        netfilter-devel@...r.kernel.org, davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] netfilter: check duplicate config when initializing
 in ipt_CLUSTERIP

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];