netdev - Re: [PATCH net-next 1/3] ipv6: fib6_info_destroy

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Message-ID: <dbd84b02-4459-74a0-c073-28c5c91383d8@gmail.com>
Date:   Tue, 23 Apr 2019 13:46:14 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Wei Wang <weiwan@...gle.com>
Subject: Re: [PATCH net-next 1/3] ipv6: fib6_info_destroy_rcu() cleanup

On 4/23/19 11:40 AM, Eric Dumazet wrote:
> I believe we have a problem with f6i->rt6i_pcpu rules :
> 
> It seems concurrent lookups can happily use it while
> the call_rcu() is ongoing before fib6_info_destroy_rcu() is finally called.
> 
> We lack proper RCU rules here. Concurrent lookups should be warned
> that the destroy operation is ongoing.
> 
> One solution could look at fib6_ref value : If it is 0, then we are
> not allowed to mess with rt6i_pcpu.

ok. I'll take a look as part of the testing I am doing for other changes.