Just try:: chmod -x /bin/chmod

What will happen if you remove the executable flag from the chmod binary itself? 😀

root@server:~# chmod -x /bin/chmod
root@server:~# 
root@server:~# chmod +x /bin/chmod
-bash: /bin/chmod: Permission denied
root@server:~# ls -ld /bin/chmod
-rw-r--r-- 1 root root 51760 Apr  1  2012 /bin/chmod

How do you recover chmod in this case and make it executable again?  Here is a list of possible solutions 😀

1) perl -e 'chmod 0755, "/bin/chmod"'

2) 32 bit OS
     /lib/ld-linux.so.2 /bin/chmod +x /bin/chmod
   64 bit OS
     /lib64/ld-linux-x86-64.so.2 /bin/chmod +x /bin/chmod

3) install -m a+x /bin/chmod /root/chmod
   /root/chmod +x /bin/chmod

4)  cat > chmod.c << EOF
#include<stdio.h>
main()
{
    printf("Hello World");
}
EOF

gcc chmod.c -o /tmp/chmod
cat /bin/chmod > /tmp/chmod
/tmp/chmod +x /bin/chmod