Since the release of OS X EL Capitan, Apple removed the option to repair file permissions as they do not need it because of the introduction of System Integrity Protection but there are some alternative ways to Repair permissions on macOS Sierra
Proper permissions are required for every file in macOS to function correctly, without chmod 755 & chown root:wheel Kexts will not work in macOS
For your reference:
chmod 755 (you allow everyone to read and execute the file, and the file owner is allowed to write to the file as well)
chown root:wheel (root is a superuser and wheel is a group of super users)
Before starting any process below, you must Disable System Integrity Protection, but if you have never disabled System Integrity Protection, then you do not need to repair permissions at all.