title: issue: sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set
body: <p>my system is ubuntu 16.04. i just want to make a test. i was login with my general account haungxin. i run commnad <code>sudo chown huangxin:huangxin sudo</code>,then run sudo show this error. and continue i run <code>su root</code> &amp; <code>chown root:root sudo</code>,i checked the property of sudo file is <code>-rwxr-xr-x 1 root root 136808 2月   1 02:37 /usr/bin/sudo</code> . but when i run sudo in general accout , it also dump error: sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set  , i don't know why that happend  i have  recoverd sudo file's property as previous and i can't find different compare to other machines's sudo file property . but why it can't work as normal. that's really confused me. i will really preciated who can it.   </p>