linux-kernel - Re: [PATCH v2] net/bridge: Use __in6_dev_get rather than in6_dev_get in br_validate

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Message-ID: <20150708090421.GA4824@salvia>
Date:	Wed, 8 Jul 2015 11:04:21 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	Julien Grall <julien.grall@...rix.com>,
	xen-devel@...ts.xenproject.org, kaber@...sh.net,
	kadlec@...ckhole.kfki.hu, davem@...emloft.net,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bernhard Thaler <bernhard.thaler@...et.at>, fw@...len.de,
	ian.campbell@...rix.com, wei.liu2@...rix.com,
	Bob Liu <bob.liu@...cle.com>
Subject: Re: [PATCH v2] net/bridge: Use __in6_dev_get rather than in6_dev_get
 in br_validate_ipv6

On Tue, Jul 07, 2015 at 11:34:34AM -0700, Stephen Hemminger wrote:
> On Tue, 7 Jul 2015 15:55:21 +0100
> Julien Grall <julien.grall@...rix.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@...rix.com>
> > Cc: Bernhard Thaler <bernhard.thaler@...et.at>
> > Cc: Pablo Neira Ayuso <pablo@...filter.org>
> > Cc: fw@...len.de
> > Cc: ian.campbell@...rix.com
> > Cc: wei.liu2@...rix.com
> > Cc: Bob Liu <bob.liu@...cle.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@...workplumber.org>

Applied, thanks.
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