Hi guys, thanks for that, i can confirm this solution works on P601 running kitkat
- installed TWRP 184.108.40.206 tar via Odin (heard the 2.7 could bug on this device)
- boot in TWRP and install UPDATE-SuperSU-v1.94 that i previously stored in my ext xd card
- straight after boot, updated super SU app via playstore
- open super SU app, accept binary update via twrp, let it do his job
- after automatic reboot, open superSU app, click no at question "do you want to disable Knox"
- reboot, do the same step but answer "yes"