netdev - Query regarding a code snippet in __inet_lookup

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Date:	Fri, 20 Jan 2012 17:02:36 -0800
From:	MuraliRaja Muniraju <muralira@...gle.com>
To:	netdev@...r.kernel.org
Subject: Query regarding a code snippet in __inet_lookup_established.

Hi All,
    In function __inet_lookup_established, I do see a potential issue
in a corner case while reading through the code where socket can be
freed while being in the list and also while in rcu_read critical
section.
        rcu_read_lock();
begin:
        sk_nulls_for_each_rcu(sk, node, &head->chain) {
                if (INET_MATCH(sk, net, hash, acookie,
                                        saddr, daddr, ports, dif)) {
                        if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
                                goto begintw;
                        if (unlikely(!INET_MATCH(sk, net, hash, acookie,
                                saddr, daddr, ports, dif))) {
Murali>                                sock_put(sk);
Murali>                                goto begin;
                        }
                        goto out;
                }
        }

I am not certain under what scenario this might occur. Can someone let
me know if this is a possibility.
-- 
Thanks,
Murali
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