Unfortunately, it turns out that some Samsung laptops will fail to boot if too much of the [UEFI] variable storage space is used. We don't know what "too much" is yet, but writing a bunch of variables from Windows is enough to trigger it. I put some sample code here — it writes out 36 variables each containing a kilobyte of random data. I ran this as an administrator under Windows and then rebooted the system. It never came back.
YurB writes: "Matthew Garret, a Linux kernel developer who was investigating the recent Linux-on-Samsung-in-UEFI-mode problem, has bricked a Samsung laptop using a test userspace program in Windows. The most fascinating part of the story is on what is actually causing the firmware boot failure: