Matthew Garrett Has a Fix To Prevent Bricked UEFI Linux Laptops

hypnosec writes "UEFI guru Matthew Garrett, who cleared the Linux kernel in Samsung laptop bricking issues, has come to rescue beleaguered users by offering a survival guide enabling them to avoid similar issues. According to Garrett, storage space constraints in UEFI storage variables is the reason Samsung laptops end up bricking themselves. Garrett said that if the storage space utilized by the UEFI firmware is more than 50 percent full, the laptop will refuse to start and ends up being bricked. To prevent this from happening, he has provided a Kernel patch."

Comments

more than 50 per cent full = fail is bad

[Joe_Dragon]

more than 50 per cent full = fail is bad and Samsung needs to come out with a bios update to fix that.

Re:more than 50 per cent full = fail is bad

[SuricouRaven]

Something like this should never have gotten through testing. Samsung must have tested using only a single OS or a closely related family (ie, Windows) - and that is no way to test if a piece of code is going to behave under all circumstances.

Re:more than 50 per cent full = fail is bad

[broken_chaos]

They didn't even test the UEFI nvram (not a partition) filling up. If they had, they would have seen that, oh, wow, it bricks the laptop entirely.

Re:more than 50 per cent full = fail is bad

[Goaway]

Remember, if Apple hasn't done anything wrong, you can take something somebody else did, and pretend they did it even worse! That's how evil Apple is!

Re:more than 50 per cent full = fail is bad

[ais523]

The same bug can brick Samsung laptops on Windows too. It's just that it was noticed on Linux first.

Re:more than 50 per cent full = fail is bad

[fuzzyfuzzyfungus]

It was probably very well intentioned - to avoid the UEFI partition becoming full and causing errors.

Are you not seeing the insanity of avoiding errors caused by being 100% full by bricking the device at 50% full?

More broadly, for what possible reason would Samsung handle UEFI storage in such a fucked-up way? How many decades now have we had computers with some sort of mass-storage device that had to be treated sanely?

Re:problem fixed?

[cheater512]

No the bricked laptops are still bricked. This just stops more laptops from falling to the same bug.

Re:Bad Unified Extensible Firmware Interface...or?

[Sir_Sri]

---The UEF Interface seems to work just fine with Win OS and iOS. How is that a bios problem?

Samsungs implementation of UEFI is the problem, not the UEFI specification. No, it's not a 'bios' problem, UEFI replaced bios, but Samsung seems to have done something odd in their implementation of UEFI.

"---Gee wonder why the great mass migration to Linux hasn't happened?

Well sure, that has always been an issue. Linux apparently isn't important enough for companies to bother testing for it, which means it only works with contrived hacks, which means no one uses it, which means companies don't think it's important enough to bother testing for it.

No...Bad Unified Extensible Firmware Interface

[tuppe666]

The UEF Interface seems to work just fine with Win OS and iOS. How is that a bios problem?

http://www.pcworld.com/article/2027819/not-just-linux-windows-can-brick-samsung-laptops-too.html No bad on Windows too.

Please don't quote other peoples comments as fact, I suggest you check out the reply to it.

As for the Mass Migration to Linux, that happened with Android, which is set to become the most installed OS this year.

Re:When you go Linux....

[Cito]

You can sometimes on many "bricked" devices like linksys router bricks after borking a dd-wrt install
and on the samsung laptops as well by playing with the jtag

http://en.wikipedia.org/wiki/Joint_Test_Action_Group

most stuff has jtag support and in some cases you can use the jtag header to unbrick a device.

I've unbricked an old WRT54GL after a screwup I did on an older dd-wrt install few years ago using jtag.

it's not something a normal user would be able to do or have confidence in doing, so yea in most cases the normal user will never unbrick.

Re:Bad Unified Extensible Firmware Interface...or?

[fluffy99]

It's been demonstrated that this bug can be elicited from Windows as well. And Windows expects to be able to write even more info than Linux was. Linux was just the first to expose the problem by trying to use UEFI variables to hold kernel panic info (Apple does something similar). IT didn't help that the UEFI driver itself caused the kernel panic, after which the kernel writes some debug log info to the UEFI to support later postmortem analysis.

It depends on the cpu and the manufacturing....

[Anonymous Coward]

procedure. Some ARM chips have bootstrap code that will talk to a usb device (i.e. looks like a serial port, sort of), and there is a program that lets you load the initial software no matter what's in flash. That usb port might just be a header or a bunch of pads on the cpu.

With other devices you have to go into a jtag port, (i.e. a header or perhaps just solder pads) load a tiny program into ram, and use THAT to program the flash.

If they build them with empty flash, there has to be a way to do the initial load. If they build them with programmed flash, it might not be possible without unsoldering the flash chip(s) or something like that.

English for Slashdot editors

[wonkey_monkey]

According to Garrett, storage space constraints in UEFI storage variables is the reason Samsung laptops end up bricking themselves.

Is? Is?