I had a similar problem. I couldn't make it executable no matter how high I raised my privileges.
Also, the recommended way in linux with the bunnypath environment variable also didn't work: the updater couldn't determine the bunny firmware and would exit.
I ended up doing a factory reset:
After that, the updater was able to detect and run.
I was still in Windows when I tried the fix, so I just used the updater there and cannot currently confirm if it would have worked in linux as well. But I had a similar symptom and a factory reset helped. Worth a shot if you're still stuck.