netdev - Re: null pointer dereference in interrupt after receiving an ip packet on veth from xsk from user space

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Message-ID: <5dde2a2f-a4cf-4ede-967d-b314ec27706f@nop.hu>
Date: Mon, 20 Oct 2025 11:18:52 +0200
From: mc36 <csmate@....hu>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Jonathan Lemon <jonathan.lemon@...il.com>,
 Stanislav Fomichev <sdf@...ichev.me>,
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 Magnus Karlsson <magnus.karlsson@...el.com>, Björn Töpel
 <bjorn@...nel.org>, 1118437@...s.debian.org, netdev@...r.kernel.org,
 bpf@...r.kernel.org
Subject: Re: null pointer dereference in interrupt after receiving an ip
 packet on veth from xsk from user space

hi,

On 10/20/25 11:04, Jason Xing wrote:
> 
> Thanks for working on this.
> 
i also appreciate that you also working on this! :)


> Strange thing is that I didn't manage to see the crash on 6.16.0-rc6,
> 6.17.0-rc3 or 6.18.0-rc1 that is the latest. I feel that your
> environment is hugely different from mine.
> 

so i managed to have the crash on 6.16.8, 6.16.9 and 6.17.2....

but 6.17.7 and below seems to be working just fine here....


> I followed your steps you attached in your code:
> ////// gcc xskInt.c -lxdp
> ////// sudo ip link add veth1 type veth
> ////// sudo ip link set veth0 up
> ////// sudo ip link set veth1 up
> ////// sudo ./a.out

exactly, thats how to trigger the crash...

> 
> The version of libxdp that I use is 1.4.2, BTW.
> 

c36@...mu:~$ dpkg -l | grep xdp
ii  librte-net-af-xdp25:amd64               24.11.3-2                    amd64        Data Plane Development Kit (librte-net-af-xdp runtime library)
ii  libxdp-dev:amd64                        1.5.7-3                      amd64        library and utilities for use with XDP - development files
ii  libxdp1:amd64                           1.5.7-3                      amd64        library and utilities for use with XDP - shared library

is what i use from the debian-sid repo....


> Could you share me with your .config? I'm not sure if I missed something.
> 
so i'm playing with debian sid kernels and libxdp, whereas the

first report came from fedora rawhide land to freertr....

btw i'm attaching the configs i had and hadn't success with....

have a nice day,

csaba

Download attachment "zzz.tar.gz" of type "application/gzip" (318734 bytes)