bpfilter: read fail 0

[Andrea Righi]

On Tue, Feb 14, 2023 at 01:24:53PM -0800, Vincent Li wrote:
> On Tue, Feb 14, 2023 at 10:08 AM Vincent Li <vincent.mc.li at gmail.com> wrote:
> >
> > Hi,
> >
> > Sorry if this is the wrong list, I installed
> > https://kernel.ubuntu.com/~kernel-ppa/mainline/v6.1.10/ on Ubuntu
> > 20.04. I have firehol running with iptables rules, the kernel emits
> > noise log messages like below all the time, google this message, it
> > appears the issue has been fixed in the upstream mainline kernel, I am

Do you have a reference / link for the specific upstream fix? I can't
find anything relevant googling the error message.

> > wondering if Ubuntu PPA kernel could address this issue.
> >
> > [   36.902856] bpfilter: Loaded bpfilter_umh pid 2242
> >
> > [   36.902998] bpfilter: read fail 0
> >
> > [   36.976678] bpfilter: Loaded bpfilter_umh pid 2244
> >
> > [   36.976795] bpfilter: read fail 0
> >
> > [   37.042831] bpfilter: Loaded bpfilter_umh pid 2246
> >
> > [   37.042990] bpfilter: read fail 0
> >
> 
> it looks the following should be disabled
> 
> CONFIG_BPFILTER=y
> 
> CONFIG_BPFILTER_UMH=m

Well.. these options have been enabled since focal, I don't think
disabling them is a viable solution.

For what I see there seem to be some interactions with the firewall
(iptables / ufw), that is triggering bpfilter user mode helper, that
seems to exit immediately after reading the request message with this
'read fail 0' error message.

I'll try to reproduce the problem and investigate more, unless you have
a reference to the commit that fixes this.

Thanks for reporting this!
-Andrea