[Letux-kernel] [PATCH RFC] net: hso: register netdev later to avoid a race condition

Andreas Kemnade andreas at kemnade.info
Wed Apr 26 07:27:21 CEST 2017


Hi,

On Wed, 26 Apr 2017 06:50:00 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
> > Am 25.04.2017 um 23:11 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > On Tue, 25 Apr 2017 15:29:53 +0200
> > "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> > 
> >> 
> >> So my conclusion is:
> >> 
> >> * dhcpd is recognising quite quickly that there is a new interface being enabled.
> >> * and tries to do some ioctl which makes the kernel segfault
> >> * and crashes dhcpd
> >> 
> >> The fix we are talking about makes this being ignored.
> >> 
> >> It might simply be that dhcpd is responding faster with an ioctl() than with older kernels.
> >> So let's keep the patch for the moment.
> >> 
> > well, i would like to replace it with something upstreamable. But maybe
> > it is best if you first send the 20ms-hack as a [PATCH RFC] together
> > with the backtrace so that we have more brains on that topic.
> > 
> > How was dhcpcd started? Just so that I can properly reproduce that.
> 
> Just apt-get install isc-dhcp-client on Jessie.
> This installs /etc/init.d/dhcpcd startup code and defaults.
> 
> No special rule(s) for hso.
> 
isc-dhcp-client is dhclient stuff.

The package name is dhcpcd5. I did not know that it does so much
stuff automatically. Starting wpa_supplicant without my permission.
That either needs to be tamed or it deserves a place on my personal
packet banlist.

But nevertheless I managed to reproduce the kernel oops.

Regards,
Andreas
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