netdev - Re: [PATCH net] sctp: check duplicate node before inserting a new transport

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Message-Id: <20170217.151907.1987368624831286456.davem@davemloft.net>
Date:   Fri, 17 Feb 2017 15:19:07 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        marcelo.leitner@...il.com, nhorman@...driver.com,
        vyasevich@...il.com
Subject: Re: [PATCH net] sctp: check duplicate node before inserting a new
 transport

From: Xin Long <lucien.xin@...il.com>
Date: Fri, 17 Feb 2017 16:35:24 +0800


> +	list = rhltable_lookup(&sctp_transport_hashtable, &arg,
> +			       sctp_hash_params);
> +
> +	rhl_for_each_entry_rcu(transport, tmp, list, node)
> +		if (transport->asoc->ep == t->asoc->ep) {
> +			err = -EEXIST;
> +			goto out;
> +		}
> +
>  	err = rhltable_insert_key(&sctp_transport_hashtable, &arg,
>  				  &t->node, sctp_hash_params);
> +
> +out:

Well, what if another thread of control inserts a matching transport
after you've checked the list but before rhltable_insert_key() does
it's work?

What write side lock is being held to protect the table from
modifications here?