netdev - Re: oops with ip6_rt_cache

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Message-ID: <4f7ab12f-37c2-5bdc-5993-be8da71ec0de@fb.com>
Date:   Sun, 26 Aug 2018 21:57:40 -0700
From:   Yonghong Song <yhs@...com>
To:     David Ahern <dsahern@...il.com>, netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>, Martin Lau <kafai@...com>,
        Dave Jones <dsj@...com>
Subject: Re: oops with ip6_rt_cache_alloc



On 8/24/18 4:04 PM, David Ahern wrote:
> 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?

We will give a try with 4.18. Thanks.