When I got mine S-OFF, I used this set of commands:
adb reboot <--important!!!!
adb wait-for-device push firewater /data/local/tmp
chmod 755 /data/local/tmp/firewater
Type them in exactly as they are above chmod first, then su, then run firewater.
At least, that's what worked for me after trying su then chmod like 50 times with no success.
Verizon HTC One (M7) - CyanogenMod 11 and NuSense6
Galaxy S3 - CyanogenMod 11
Kindle Fire 1st Gen - CyanogenMod 11 SGT7