netdev - Re: [PATCH v2 2/3] net: Add BUG_ON() to get

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Date:   Tue, 09 Jan 2018 10:52:22 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>, netdev@...r.kernel.org,
        davem@...emloft.net
Cc:     ebiederm@...ssion.com
Subject: Re: [PATCH v2 2/3] net: Add BUG_ON() to get_net()

On Tue, 2018-01-09 at 18:00 +0300, Kirill Tkhai wrote:
> Since people may mistakenly obtain destroying net
> from net_namespace_list and from net::netns_ids
> without checking for its net::counter, let's protect
> against such situations and insert BUG_ON() to stop
> move on after this.
> 
> Panic is better, than memory corruption and undefined
> behavior.
> 
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
> ---
>  include/net/net_namespace.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index 10f99dafd5ac..ff0e47471d5b 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -195,7 +195,7 @@ void __put_net(struct net *net);
>  
>  static inline struct net *get_net(struct net *net)
>  {
> -	atomic_inc(&net->count);
> +	BUG_ON(atomic_inc_return(&net->count) <= 1);
>  	return net;
>  }


Why not simply use refcount_t instead of duplicating its logic ?