If you plan to remix the remix you will need:
permission from the original copyright owner, usually the publisher or songwriter
as a minimum.
If YOU use samples from the original recording you will need permission from the recording/mechanical copyright owner, usually the record label or artist
If you plan to use elements of the remix arrangement you will need permission for that, usually from the publisher.
If you plan to use samples of the remix recording you will need permission from the recording copyright owner, usually the record label
if the remixer is unsigned in either capacity you will need permission from the remixer for both using their arrangement and for using samples.