Re: net/ipv6: GPF in rt6_ifdown

[Cong Wang]

On Wed, Jun 21, 2017 at 10:53 AM, Andrey Konovalov
<andreyknvl@xxxxxxxxxx> wrote:
> On Wed, Jun 21, 2017 at 3:09 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>> On Wed, Jun 21, 2017 at 2:08 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>>> Hi,
>>>
>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>
>>> On commit 9705596d08ac87c18aee32cc97f2783b7d14624e (4.12-rc6+).
>>>
>>> It might be related to:
>>> https://groups.google.com/forum/#!topic/syzkaller/ZJaqAiFLe3k
>>>
>>> I only have a reproducer in the form of a syzkaller program, attached
>>> together with my .config.
>>
>> I now have a C reproducer as well, attached.
>
> And here's a much simpler reproducer.

Thanks a lot for your reproducer!

I added a few printk's, and find that we somehow have rt->rt6i_idev set
to NULL but still keep it in the uncached list. ip6_dst_destroy() unlinks
it before NULL'ing, so it should not be that case.