From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v2] net/bridge: Use __in6_dev_get rather than
 in6_dev_get in br_validate_ipv6
Date: Tue, 7 Jul 2015 11:34:34 -0700
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To: Julien Grall <julien.grall@citrix.com>
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On Tue, 7 Jul 2015 15:55:21 +0100
Julien Grall <julien.grall@citrix.com> wrote:

> The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
> forward IPv6 fragmented packets" introduced a new function
> br_validate_ipv6 which take a reference on the inet6 device. Although,
> the reference is not released at the end.
> 
> This will result to the impossibility to destroy any netdevice using
> ipv6 and bridge.
> 
> It's possible to directly retrieve the inet6 device without taking a
> reference as all netfilter hooks are protected by rcu_read_lock via
> nf_hook_slow.
> 
> Spotted while trying to destroy a Xen guest on the upstream Linux:
> "unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> Cc: Bernhard Thaler <bernhard.thaler@wvnet.at>
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: fw@strlen.de
> Cc: ian.campbell@citrix.com
> Cc: wei.liu2@citrix.com
> Cc: Bob Liu <bob.liu@oracle.com>
> 
> ---
>     Note that it's impossible to create new guest after this message.
>     I'm not sure if it's normal.
> 
>     Changes in v2:
>         - Don't take a reference to inet6.
>         - This was "net/bridge: Add missing in6_dev_put in
>         br_validate_ipv6" [0]
> 
>     [0] https://lkml.org/lkml/2015/7/3/443
> ---
>  net/bridge/br_netfilter_ipv6.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

I like this simple solution

Acked-by: Stephen Hemminger <stephen@networkplumber.org>