netdev - Re: 4.1.0, kernel panic, pppoe

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Date:	Tue, 22 Sep 2015 04:47:48 +0300
From:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
To:	Guillaume Nault <g.nault@...halink.fr>
Cc:	Dan Williams <dcbw@...hat.com>, Netdev <netdev@...r.kernel.org>,
	ebiederm@...ssion.com, davem@...emloft.net, simon@...nz.org.uk,
	develop@...stov.de
Subject: Re: 4.1.0, kernel panic, pppoe_release

Hi,
Sorry for late reply, was not able to push new kernel on pppoes without 
permissions (it's production servers), just got OK.

I am testing patch on another pppoe server with 9k users, for ~3 days, 
seems fine. I will test today
also on server that was experiencing crashes within 1 day.

On 2015-09-10 18:56, Guillaume Nault wrote:
> On Fri, Jul 17, 2015 at 09:16:14PM +0300, Denys Fedoryshchenko wrote:
>> Probably my knowledge of kernel is not sufficient, but i will try few
>> approaches.
>> One of them to add to pppoe_unbind_sock_work:
>> 
>>         pppox_unbind_sock(sk);
>>         +/* Signal the death of the socket. */
>>         +sk->sk_state = PPPOX_DEAD;
>> 
> I don't believe this will fix anything. pppox_unbind_sock() already
> sets sk->sk_state when necessary.
> 
>> I will wait first, to make sure this patch was causing kernel panic 
>> (it
>> needs 24h testing cycle), then i will try this fix.
>> 
> I suspect the problem goes with actions performed on the underlying
> interface (MAC address, MTU or link state update). This triggers
> pppoe_flush_dev(), which cleans up the device without announcing it
> in sk->sk_state.
> 
> Can you pleas try the following patch?
> 
> ---
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 3837ae3..2ed7506 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -313,7 +313,6 @@ static void pppoe_flush_dev(struct net_device *dev)
>  			if (po->pppoe_dev == dev &&
>  			    sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND | PPPOX_ZOMBIE)) 
> {
>  				pppox_unbind_sock(sk);
> -				sk->sk_state = PPPOX_ZOMBIE;
>  				sk->sk_state_change(sk);
>  				po->pppoe_dev = NULL;
>  				dev_put(dev);
--
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