netdev - Re: [PATCHv2 net] ipv6: make ip6_create_rt_rcu return ip6_null

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Date:   Wed, 20 Mar 2019 11:07:51 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, weiwan@...gle.com, dsahern@...il.com,
        pabeni@...hat.com
Subject: Re: [PATCHv2 net] ipv6: make ip6_create_rt_rcu return
 ip6_null_entry instead of NULL

From: Xin Long <lucien.xin@...il.com>
Date: Wed, 20 Mar 2019 14:45:48 +0800

> Jianlin reported a crash:
> 
>   [  381.484332] BUG: unable to handle kernel NULL pointer dereference at 0000000000000068
>   [  381.619802] RIP: 0010:fib6_rule_lookup+0xa3/0x160
>   [  382.009615] Call Trace:
>   [  382.020762]  <IRQ>
>   [  382.030174]  ip6_route_redirect.isra.52+0xc9/0xf0
>   [  382.050984]  ip6_redirect+0xb6/0xf0
>   [  382.066731]  icmpv6_notify+0xca/0x190
>   [  382.083185]  ndisc_redirect_rcv+0x10f/0x160
>   [  382.102569]  ndisc_rcv+0xfb/0x100
>   [  382.117725]  icmpv6_rcv+0x3f2/0x520
>   [  382.133637]  ip6_input_finish+0xbf/0x460
>   [  382.151634]  ip6_input+0x3b/0xb0
>   [  382.166097]  ipv6_rcv+0x378/0x4e0
> 
> It was caused by the lookup function __ip6_route_redirect() returns NULL in
> fib6_rule_lookup() when ip6_create_rt_rcu() returns NULL.
> 
> So we fix it by simply making ip6_create_rt_rcu() return ip6_null_entry
> instead of NULL.
> 
> v1->v2:
>   - move down 'fallback:' to make it more readable.
> 
> Fixes: e873e4b9cc7e ("ipv6: use fib6_info_hold_safe() when necessary")
> Reported-by: Jianlin Shi <jishi@...hat.com>
> Suggested-by: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Applied and queued up for -stable, thanks.