In this case, an evil system administrator could change the text of /proc/kallsyms (probably via a hacked libc and LD_PRELOAD, or just the hacked libc) and then execute arbitrary code as you, because the exploit code uses an unchecked write into a stack variable (and who compiles their exploit code with a stack protector).

I am almost tempted to do this, use the exploit to get root on my work machines, and then replace the libc... just to see if anyone else tries the exploit. (Note to the literal: not really.)

execv("/bin/sh -c 'for i in `find $HOME`; do echo "rm -f $i"; done', 0);