netdev - Re: [PATCH net] dccp: don't restart ccid2_hc_tx_rto

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Date:   Thu, 25 Jan 2018 10:03:47 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexey Kodanev <alexey.kodanev@...cle.com>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>, dccp@...r.kernel.org
Subject: Re: [PATCH net] dccp: don't restart ccid2_hc_tx_rto_expire() if sk
 in closed state

On Thu, 2018-01-25 at 20:43 +0300, Alexey Kodanev wrote:
> ccid2_hc_tx_rto_expire() timer callback always restarts the timer
> again and can run indefinitely (unless it is stopped outside), and
> after commit 120e9dabaf55 ("dccp: defer ccid_hc_tx_delete() at
> dismantle time"), which moved sk_stop_timer() to sk_destruct(),
> this started to happen quite often. The timer prevents releasing
> the socket, as a result, sk_destruct() won't be called.
> 
> Found with LTP/dccp_ipsec tests running on the bonding device,
> which later couldn't be unloaded after the tests were completed:
> 
>   unregister_netdevice: waiting for bond0 to become free. Usage count = 148
> 
> Fixes: 120e9dabaf55 ("dccp: defer ccid_hc_tx_delete() at dismantle time")
> Signed-off-by: Alexey Kodanev <alexey.kodanev@...cle.com>
> ---

I understand your fix, but not why commit 120e9dabaf55 is bug origin.

Looks like this always had been buggy : Timer logic should have checked
socket state from day 0.

I did not move sk_stop_timer() to sk_destruct()