From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [Patch net] ipv6: avoid unregistering inet6_dev for loopback
Date: Thu, 22 Jun 2017 13:22:32 -0400 (EDT)
Message-ID: <20170622.132232.558497530705704974.davem@davemloft.net>
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Cc: netdev@vger.kernel.org, andreyknvl@google.com, dlezcano@fr.ibm.com,
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To: xiyou.wangcong@gmail.com
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From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Wed, 21 Jun 2017 14:34:58 -0700

> The per netns loopback_dev->ip6_ptr is unregistered and set to
> NULL when its mtu is set to smaller than IPV6_MIN_MTU, this
> leads to that we could set rt->rt6i_idev NULL after a
> rt6_uncached_list_flush_dev() and then crash after another
> call.
> 
> In this case we should just bring its inet6_dev down, rather
> than unregistering it, at least prior to commit 176c39af29bc
> ("netns: fix addrconf_ifdown kernel panic") we always
> override the case for loopback.
> 
> Thanks a lot to Andrey for finding a reliable reproducer.
> 
> Fixes: 176c39af29bc ("netns: fix addrconf_ifdown kernel panic")
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: Daniel Lezcano <dlezcano@fr.ibm.com>
> Cc: David Ahern <dsahern@gmail.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied and queued up for -stable.