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: <CAL+tcoDLr_soUTsZzFE+f-M0R83tvqx7tGjU+a5nBFSdtyP7Lw@mail.gmail.com>
Date: Tue, 21 Oct 2025 20:25:09 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Fernando Fernandez Mancera <fmancera@...e.de>
Cc: mc36 <csmate@....hu>, alekcejk@...glemail.com, 
	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

On Tue, Oct 21, 2025 at 6:52 PM Fernando Fernandez Mancera
<fmancera@...e.de> wrote:
>
>
>
> On 10/20/25 11:31 PM, mc36 wrote:
> > hi,
> >
> > On 10/20/25 11:04, Jason Xing wrote:
> >>
> >> 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
> >
> > ip link set dev veth1 address 3a:10:5c:53:b3:5c
> >
> >> ////// sudo ./a.out
> >>
> > that will do the trick on a recent kerlek....
> >
> > its the destination mac in the c code....
> >
> > ps: chaining in the original reporter from the fedora land.....
> >
> >
> > have a nice day,
> >
> > cs
> >
> >
>
> hi, FWIW I have reproduced this and I bisected it, issue was introduced
> at 30f241fcf52aaaef7ac16e66530faa11be78a865 - working on a patch.

Exactly. I simply reverted it and its dependencies and didn't see any
crash then. It was newly introduced, hopefully it will not bring much
trouble. As I replied before, I will take a look tomorrow morning.

Thanks,
Jason