netdev - Re: [PATCH net v2] ipv6: remove null_entry before adding default route

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Message-Id: <20180109.123436.874984116978793472.davem@davemloft.net>
Date:   Tue, 09 Jan 2018 12:34:36 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     weiwan@...gle.com
Cc:     netdev@...r.kernel.org, kafai@...com, edumazet@...gle.com
Subject: Re: [PATCH net v2] ipv6: remove null_entry before adding default
 route

From: Wei Wang <weiwan@...gle.com>
Date: Mon,  8 Jan 2018 10:34:00 -0800

> From: Wei Wang <weiwan@...gle.com>
> 
> In the current code, when creating a new fib6 table, tb6_root.leaf gets
> initialized to net->ipv6.ip6_null_entry.
> If a default route is being added with rt->rt6i_metric = 0xffffffff,
> fib6_add() will add this route after net->ipv6.ip6_null_entry. As
> null_entry is shared, it could cause problem.
> 
> In order to fix it, set fn->leaf to NULL before calling
> fib6_add_rt2node() when trying to add the first default route.
> And reset fn->leaf to null_entry when adding fails or when deleting the
> last default route.
> 
> syzkaller reported the following issue which is fixed by this commit:
 ...
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Fixes: 66f5d6ce53e6 ("ipv6: replace rwlock with rcu and spinlock in fib6_table")
> Signed-off-by: Wei Wang <weiwan@...gle.com>

Applied, thank you.