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: <aQ9YhCAdu7QNyYxu@eldamar.lan>
Date: Sat, 8 Nov 2025 15:49:40 +0100
From: Salvatore Bonaccorso <carnil@...ian.org>
To: Fernando Fernandez Mancera <fmancera@...e.de>
Cc: mc36 <csmate@....hu>, Jason Xing <kerneljasonxing@...il.com>,
	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

Hi,

On Tue, Oct 21, 2025 at 12:51:32PM +0200, Fernando Fernandez Mancera 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.

Just a qustion in particular for the stable series shipping the commit
(now only 6.17.y relevant at this point since 6.16.y is EOL): Give the
proper fix will take a bit more time to develop, would it make sense
to at least revert the offending commit in the stable series as the
issue is, unless I missunderstood the report, remotely(?) triggerable
denial of service? 

Or do I miss something here?

Regards,
Salvatore