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Re: [DNG] Linux system can be brought down by sending SIGILL to Systemd - PID 1 is killed it seems




On Sat, 25 May 2019 00:21:07 +0200
arne <sp113438@xxxxxxxxxx> wrote:

> On Fri, 24 May 2019 23:43:49 +0200
> arne <sp113438@xxxxxxxxxx> wrote:
> 
> > On Fri, 24 May 2019 14:01:35 -0700
> > Fred <fred@xxxxxxxxxxxx> wrote:
> >   
> > > Hello,
> > > I subscribe to the Devuan Linux mailing list.  This posting just
> > > arrived and it appears quite important to Debian.
> > > 
> > > -------- Forwarded Message --------
> > > Subject: 	[DNG] Linux system can be brought down by sending
> > > SIGILL to Systemd
> > > Date: 	Fri, 24 May 2019 22:04:34 +0200
> > > From: 	Martin Steigerwald <martin@xxxxxxxxxxxx>
> > > To: 	DNG <dng@xxxxxxxxxxxxxx>
> > > 
> > > 
> > > 
> > > Hi!
> > > 
> > > Today in a Linux training a participant attempted to bring down
> > > Debian workstation with Systemd by sending signals to PID 1 as I
> > > invited them to try to bring down PID 1 while thinking for myself
> > > that this would not be possible from my past experiences about
> > > trying to bring down PID 1 – init – myself.    
> > 
> > # while true; do kill -ILL 1 ; echo -n "." ;  sleep 0.5 ; done
> > ...........................^C
> > 
> > no problem here
> > kernel 5.1.4 stretch amd64 with systemd
> >   
> 
> Perhaps that test was a little too short so I let it run a little
> longer:
> 
> # while true; do kill -ILL 1 ; echo -n "." ;  sleep 0.5 ; done
> ..................................................................................................................................................................................................................................................................................................................................................................................................................................................^C
> 
> again no problem here.
> 
> I had no fear to run the script as I use systemd, so I know how to
> use the SysReq keys very well ;)
> 
> 
> 

# while true; do kill -ILL 1 ; echo -n "." ;  sleep 0.5 ; done

I found out PID 1 is killed when I tried to reboot:
# reboot
Failed to open /dev/initctl: No such device or address
Failed to talk to init daemon.

So I will have to use SysReq keys