From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net 3/3] ipv6: Fix dst_entry refcnt bugs in ip6_tunnel
Date: Tue, 01 Sep 2015 14:26:58 -0700
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Cc: netdev <netdev@vger.kernel.org>,
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To: Martin KaFai Lau <kafai@fb.com>
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On Tue, 2015-09-01 at 13:55 -0700, Martin KaFai Lau wrote:
> On Tue, Sep 01, 2015 at 01:14:20PM -0700, Eric Dumazet wrote:
> > It should not be a problem. refcnt is taken when/if necessary (skb
> > queued on a qdisc for example)
> >
> > We have other uses of skb_dst_set_noref()
> >
> > Please describe the problem ?
> The current ip6_tnl_dst_get() does not take the dst refcnt.
> 
> If the dst is released after ip6_tnl_dst_get() and before
> skb_dst_set_noref(), would it cause an issue?

We are under rcu here, and a dst in a cache is protected by RCU by
definition.

skb_dst_set_noref() has following debugging clause, does it trigger for
you ?

WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());