Subject: Re: [linux-next] oops in ip_route_input_noref

From: David Ahern <[email-masked]>
Date: Wed, 16 Sep 2015 07:07:42 -0600

On 9/16/15 5:50 AM, Richard Alpe wrote:
> On 2015-09-16 11:24, Sergey Senozhatsky wrote:
>> Hi,
>>
>> 4.3.0-rc1-next-20150916
>>
>> oops after removal of rndis usb device

Hi Sergey:

Is this with KVM or baremetal?

-----8<-----
thanks for the analysis

>> addr2line -e vmlinux -i 0xffffffff8146c0b1
>> net/ipv4/route.c:1815
>> net/ipv4/route.c:1905
>>
>>
>> which seems to be this line ip_route_input_noref()->ip_route_input_slow():
>> ...
>> 1813         rth->rt_is_input = 1;
>> 1814         if (res.table)
>> 1815                 rth->rt_table_id = res.table->tb_id;
>> 1816
>> ...
>>
>>
>> added by b7503e0cdb5dbec5d201aa69d8888c14679b5ae8
>>
>>      net: Add FIB table id to rtable
>>
>>      Add the FIB table id to rtable to make the information available for
>>      IPv4 as it is for IPv6.
>>
>>
>> 	-ss

Hi Richard:

> I to get an Oops in ip_route_input_noref(). It happens occasionally during bootup.
> KVM environment using virtio driver. Let me know if you need any additional info or
> if you want me to try to bisect it.
>
> Starting network...
> ...
> [    0.877040] BUG: unable to handle kernel NULL pointer dereference at 0000000000000056
> [    0.877597] IP: [<ffffffff8155b5e2>] ip_route_input_noref+0x1a2/0xb00

Can you send me your kernel config and qemu command line? KVM with 
virtio networking is a primary test vehicle, and I did not encounter 
this at all.

Thanks,
David