[PATCH 4/4] [RFC] staging/net: move AF_X25 into drivers/staging

Martin Schiller ms at dev.tdt.de
Tue Dec 10 08:59:29 UTC 2019

On 2019-12-09 20:26, Arnd Bergmann wrote:
> On Mon, Dec 9, 2019 at 7:29 PM David Miller <davem at davemloft.net> 
> wrote:
>> From: Arnd Bergmann <arnd at arndb.de>
>> Date: Mon,  9 Dec 2019 16:12:56 +0100
>> > syzbot keeps finding issues in the X.25 implementation that nobody is
>> > interested in fixing.  Given that all the x25 patches of the past years
>> > that are not global cleanups tend to fix user-triggered oopses, is it
>> > time to just retire the subsystem?
>> I have a bug fix that I'm currently applying to 'net' right now 
>> actually:
>>         https://patchwork.ozlabs.org/patch/1205973/
>> So your proposal might be a bit premature.
> Ok, makes sense. Looking back in the history, I also see other bugfixes
> from the same author.
> Adding Martin Schiller to Cc: for a few questions:
> - What hardware are you using for X.25?

I would say that X.25 is (at least in Germany) not dead yet. For 
example, it is
still used in the railway network of the Deutsche Bahn AG in many 
areas. [1]

We deliver products for this and use the Linux X.25 stack with some 
and extensions that I would like to get upstream.

As hardware/interfaces we use X.21bis/G.703 adapters, which are 
connected via
HDLC_X25 and LAPB. Also for this there are extensions and bugfixes, 
which I
would like to include in the kernel.

> - Would you be available to be listed in the MAINTAINERS file
>   as a contact for net/x25?

Yes, you can add me to the MAINTAINERS file.
I have only limited time, but I will try to follow all requests 
concerning this

> - Does your bug fix address the latest issue found by syzbot[1],
>   or do you have an idea to fix it if not?

I don't have a direct solution for the concrete problem mentioned above, 
but at
first sight I would say that the commit 95d6ebd53c79 ("net/x25: fix
use-after-free in x25_device_event()") holds the wrong lock 
Shouldn't this be the lock &x25_neigh_list_lock as in x25_get_neigh(), 
x25_neigh_hold() is called?

>         Arnd
> [1]
> https://lore.kernel.org/netdev/CAK8P3a0LdF+aQ1hnZrVKkNBQaum0WqW1jyR7_Eb+JRiwyHWr6Q@mail.gmail.com/

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