netdev - Re: Repeatable inet6_dump_fib crash in stock 4.12.0-rc4+

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Date:   Tue, 06 Jun 2017 21:19:26 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Ben Greear <greearb@...delatech.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: Repeatable inet6_dump_fib crash in stock 4.12.0-rc4+

On Tue, 2017-06-06 at 18:34 -0600, David Ahern wrote:
> On 6/6/17 6:27 PM, Eric Dumazet wrote:
> > Good catch, but it looks like similar fix is needed a few lines before.
> > 
> > diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> > index deea901746c8570c5e801e40592c91e3b62812e0..b214443dc8346cef3690df7f27cc48a864028865 100644
> > --- a/net/ipv6/ip6_fib.c
> > +++ b/net/ipv6/ip6_fib.c
> > @@ -372,12 +372,13 @@ static int fib6_dump_table(struct fib6_table *table, struct sk_buff *skb,
> >  
> >  		read_lock_bh(&table->tb6_lock);
> >  		res = fib6_walk(net, w);
> > -		read_unlock_bh(&table->tb6_lock);
> >  		if (res > 0) {
> >  			cb->args[4] = 1;
> >  			cb->args[5] = w->root->fn_sernum;
> >  		}
> > +		read_unlock_bh(&table->tb6_lock);
> 
> indeed. tunnel vision on Ben's problem

BTW, bug was already Ben's problem when Patrick tried to fix it
in commit 2bec5a369ee79 ("ipv6: fib: fix crash when changing large fib
while dumping it")  seven years ago ;)