skb_over_panic using UDP and 6lowpan / fakelb

skb_over_panic using UDP and 6lowpan / fakelb

[David Palma]

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Hi,

Sending a simple UDP packet (39 bytes long), over a 6lowpan interface
(using fakelb), creates a kernel panic (skb_over_panic).

Steps to reproduce, and more details, can be found in:
https://github.com/PalmaITEM/6lowpan-skb_over_panic

This bug has been reported in
https://bugzilla.kernel.org/show_bug.cgi?id=195059

I have found that lengths around 39 bytes can also trigger this
behaviour and that longer packets are handled without problem.

Verified in:

- Linux version 4.9.0-0.bpo.2-amd64 (debian-kernel@lists.debian.org)
(gcc version 4.9.2 (Debian 4.9.2-10) ) #1 SMP Debian 4.9.13-1~bpo8+1
(2017-02-27)
- Linux version 4.10.4-1-ARCH (builduser@tobias) (gcc version 6.3.1
20170306 (GCC) ) #1 SMP PREEMPT Sat Mar 18 19:39:18 CET 2017


I am not familiar with the process of reporting kernel bugs, so
apologies beforehand. I am also available to provide any missing
information.

Cheers,
-- 
David Palma


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Re: skb_over_panic using UDP and 6lowpan / fakelb

[Cong Wang]

(Cc'ing netdev and maintainers)

On Mon, Mar 27, 2017 at 2:16 AM, David Palma <david.palma@ntnu.no> wrote:
>
> Hi,
>
> Sending a simple UDP packet (39 bytes long), over a 6lowpan interface
> (using fakelb), creates a kernel panic (skb_over_panic).
>
> Steps to reproduce, and more details, can be found in:
> https://github.com/PalmaITEM/6lowpan-skb_over_panic
>
> This bug has been reported in
> https://bugzilla.kernel.org/show_bug.cgi?id=195059
>
> I have found that lengths around 39 bytes can also trigger this
> behaviour and that longer packets are handled without problem.
>
> Verified in:
>
> - Linux version 4.9.0-0.bpo.2-amd64 (debian-kernel@lists.debian.org)
> (gcc version 4.9.2 (Debian 4.9.2-10) ) #1 SMP Debian 4.9.13-1~bpo8+1
> (2017-02-27)
> - Linux version 4.10.4-1-ARCH (builduser@tobias) (gcc version 6.3.1
> 20170306 (GCC) ) #1 SMP PREEMPT Sat Mar 18 19:39:18 CET 2017
>
>
> I am not familiar with the process of reporting kernel bugs, so
> apologies beforehand. I am also available to provide any missing
> information.
>
> Cheers,
> --
> David Palma
>

Re: skb_over_panic using UDP and 6lowpan / fakelb

[Alexander Aring]

Hi,

sorry for the late reply.

On 04/03/2017 07:29 PM, Cong Wang wrote:
> (Cc'ing netdev and maintainers)
> 
> On Mon, Mar 27, 2017 at 2:16 AM, David Palma <david.palma@ntnu.no> wrote:
>>
>> Hi,
>>
>> Sending a simple UDP packet (39 bytes long), over a 6lowpan interface
>> (using fakelb), creates a kernel panic (skb_over_panic).
>>
>> Steps to reproduce, and more details, can be found in:
>> https://github.com/PalmaITEM/6lowpan-skb_over_panic
>>
>> This bug has been reported in
>> https://bugzilla.kernel.org/show_bug.cgi?id=195059
>>
>> I have found that lengths around 39 bytes can also trigger this
>> behaviour and that longer packets are handled without problem.
>>
>> Verified in:
>>
>> - Linux version 4.9.0-0.bpo.2-amd64 (debian-kernel@lists.debian.org)
>> (gcc version 4.9.2 (Debian 4.9.2-10) ) #1 SMP Debian 4.9.13-1~bpo8+1
>> (2017-02-27)
>> - Linux version 4.10.4-1-ARCH (builduser@tobias) (gcc version 6.3.1
>> 20170306 (GCC) ) #1 SMP PREEMPT Sat Mar 18 19:39:18 CET 2017
>>
>>
>> I am not familiar with the process of reporting kernel bugs, so
>> apologies beforehand. I am also available to provide any missing
>> information.
>>

I will try to reproduce the failure with an x86_64 qemu virtual machine.
Myself I use a 32 Bit qemu machine because I have a dependency on
userspace software which use x86 assembler (somebody should change it to
setjmp/longjmp)... it's the RIOT-OS native plattform. I use some cross
compiling environment which doesn't support multilib yet, so I used
always 32 Bit.

btw: the github stuff is very useful and thanks for the hard work! I am
on it to reproduce it. I will report when I have more information.

- Alex