netdev - Re: [PATCH 1/3] netns: Fix icmp shutdown.

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Date:	Fri, 20 Feb 2009 18:57:02 +0300
From:	"Denis V. Lunev" <den@...nvz.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Containers <containers@...ts.osdl.org>,
	netdev@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH 1/3] netns: Fix icmp shutdown.

Acked-by: Denis V. Lunev <den@...nvz.org>

On Fri, 2009-02-20 at 07:52 -0800, Eric W. Biederman wrote:
> Recently I had a kernel panic in icmp_send during a network namespace
> cleanup.  There were packets in the arp queue that failed to be sent
> and we attempted to generate an ICMP host unreachable message, but
> failed because icmp_sk_exit had already been called.
> 
> The network devices are removed from a network namespace and their
> arp queues are flushed before we do attempt to shutdown subsystems
> so this error should have been impossible.
> 
> It turns out icmp_init is using register_pernet_device instead
> of register_pernet_subsys.  Which resulted in icmp being shut down
> while we still had the possibility of packets in flight, making
> a nasty NULL pointer deference in interrupt context possible.
> 
> Changing this to register_pernet_subsys fixes the problem in
> my testing.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
> ---
>  net/ipv4/icmp.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 382800a..3f50807 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -1207,7 +1207,7 @@ static struct pernet_operations __net_initdata icmp_sk_ops = {
>  
>  int __init icmp_init(void)
>  {
> -	return register_pernet_device(&icmp_sk_ops);
> +	return register_pernet_subsys(&icmp_sk_ops);
>  }
>  
>  EXPORT_SYMBOL(icmp_err_convert);

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