netdev - Re: [PATCH 1/2] neigh: fix possible DoS due to net iface start/stop loop

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Date:   Mon, 1 Aug 2022 09:08:37 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>,
        netdev@...r.kernel.org
Cc:     "Denis V. Lunev" <den@...nvz.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yajun Deng <yajun.deng@...ux.dev>,
        Roopa Prabhu <roopa@...dia.com>, linux-kernel@...r.kernel.org,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Konstantin Khorenko <khorenko@...tuozzo.com>, kernel@...nvz.org
Subject: Re: [PATCH 1/2] neigh: fix possible DoS due to net iface start/stop
 loop

On 7/29/22 4:35 AM, Alexander Mikhalitsyn wrote:
> The patch proposed doing very simple thing. It drops only packets from

it does 2 things - adds a namespace check and a performance based change
with the way the list is walked.

> the same namespace in the pneigh_queue_purge() where network interface
> state change is detected. This is enough to prevent the problem for the
> whole node preserving original semantics of the code.
> 


> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 54625287ee5b..213ec0be800b 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c

> @@ -386,8 +396,7 @@ static int __neigh_ifdown(struct neigh_table *tbl, struct net_device *dev,
>  	neigh_flush_dev(tbl, dev, skip_perm);
>  	pneigh_ifdown_and_unlock(tbl, dev);
>  
> -	del_timer_sync(&tbl->proxy_timer);

why are you removing this line too?

> -	pneigh_queue_purge(&tbl->proxy_queue);
> +	pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev));
>  	return 0;
>  }
>