netdev - Re: [PATCH net] ipv6: use fib6_info_hold

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Date:   Mon, 23 Jul 2018 11:19:55 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     weiwan@...gle.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, dsahern@...il.com,
        kafai@...com
Subject: Re: [PATCH net] ipv6: use fib6_info_hold_safe() when necessary

From: Wei Wang <weiwan@...gle.com>
Date: Sat, 21 Jul 2018 20:56:32 -0700

> From: Wei Wang <weiwan@...gle.com>
> 
> In the code path where only rcu read lock is held, e.g. in the route
> lookup code path, it is not safe to directly call fib6_info_hold()
> because the fib6_info may already have been deleted but still exists
> in the rcu grace period. Holding reference to it could cause double
> free and crash the kernel.
> 
> This patch adds a new function fib6_info_hold_safe() and replace
> fib6_info_hold() in all necessary places.
> 
> Syzbot reported 3 crash traces because of this. One of them is:
 ...
> Fixes: 93531c674315 (net/ipv6: separate handling of FIB entries from dst based routes)
> Reported-by: syzbot+902e2a1bcd4f7808cef5@...kaller.appspotmail.com
> Reported-by: syzbot+8ae62d67f647abeeceb9@...kaller.appspotmail.com
> Reported-by: syzbot+3f08feb14086930677d0@...kaller.appspotmail.com
> Signed-off-by: Wei Wang <weiwan@...gle.com>
> Acked-by: Eric Dumazet <edumazet@...gle.com>

Applied, thank you.