netdev - Re: [PATCH] net: Protect iterations over net::fib_notifier_ops in fib_seq

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Message-Id: <20171115.141249.80029990010099794.davem@davemloft.net>
Date:   Wed, 15 Nov 2017 14:12:49 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     ktkhai@...tuozzo.com
Cc:     jiri@...lanox.com, idosch@...lanox.com, vvs@...tuozzo.com,
        kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] net: Protect iterations over net::fib_notifier_ops in
 fib_seq_sum()

From: Kirill Tkhai <ktkhai@...tuozzo.com>
Date: Tue, 14 Nov 2017 16:51:56 +0300

> There is at least unlocked deletion of net->ipv4.fib_notifier_ops
> from net::fib_notifier_ops:
> 
> ip_fib_net_exit()
>   rtnl_unlock()
>   fib4_notifier_exit()
>     fib_notifier_ops_unregister(net->ipv4.notifier_ops)
>       list_del_rcu(&ops->list)
> 
> So fib_seq_sum() can't use rtnl_lock() only for protection.
> 
> The possible solution could be to use rtnl_lock()
> in fib_notifier_ops_unregister(), but this adds
> a possible delay during net namespace creation,
> so we better use rcu_read_lock() till someone
> really needs the mutex (if that happens).
> 
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>

Applied.