From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsahern@gmail.com>
Subject: Re: oops with ip6_rt_cache_alloc
Date: Fri, 24 Aug 2018 17:04:28 -0600
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To: Yonghong Song <yhs@fb.com>, netdev <netdev@vger.kernel.org>,
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        Dave Jones <dsj@fb.com>
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On 8/24/18 4:26 PM, Yonghong Song wrote:
> Hi,
> 
> We got a kernel oops with the following stack trace:
> 
> CPU: 24 PID: 0 Comm: swapper/24 Not tainted
> 4.16.0-10_fbk1_1183_g7e4ee4c8171c #10
> "Hardware name: Quanta Leopard-DDR3/Leopard-DDR3, BIOS F06_3A16.DDR3
> 11/19/2015"
> RIP: 0010:ip6_rt_get_dev_rcu+0x6/0x60
> RSP: 0018:ffff88046fb03c78 EFLAGS: 00010286
> RAX: 0000000040000003 RBX: ffff88035a6c1500 RCX: ffffffff81ec5dc0
> RDX: ffff88033192a090 RSI: ffff88033192a0a0 RDI: 0000000000000000

RDI = 0 means the rt passed to ip6_rt_get_dev_rcu is NULL. I believe
that can't happen prior to the fib6_info changes. After the fib6_info
changes, it means the 'from' is NULL and that is not expected.

...

> Our internal experiments showed that an early version of 4.16 works fine
> and after backporting some ipv6 route related changes and the above
> problem showed up.

Can you run the test on 4.18?