Re: [gentoo-dev] newsitem: openrc-0.28 mounts efivars read only

[Mike Gilbert]

On Thu, Jul 13, 2017 at 10:58 AM, Andrew Savchenko <bircoph@g.o> wrote:
> On Thu, 13 Jul 2017 10:29:06 -0400 Mike Gilbert wrote:
>> On Thu, Jul 13, 2017 at 7:35 AM, M. J. Everitt <m.j.everitt@×××.org> wrote:
>> > On 13/07/17 12:09, Rich Freeman wrote:
>> >> Presumably you'd only want to remount it if it was mounted ro to
>> >> start, since it sounds like openrc will be diverging from systemd
>> >> behavior here.
>> >>
>> >> While it seems like a good idea I'm not sure how big an improvement it
>> >> is in the larger scheme.  We're worried about root accidentially
>> >> modifying efivars, but we have no safeguards against root writing to
>> >> /dev/sda, and the latter seems much more likely to cause harm, and is
>> >> harder to fix.
>> >>
>> > In case you weren't aware, Rich, rewriting the efivars actually writes
>> > to the system BIOS, which renders the computer completely unbootable ..
>> > not quite the same as erasing the boot sector of your hard disk, where
>> > you simply plug in another device, and Off you go ...
>> >
>>
>> We are actually talking about protecting people who run something like
>> rm -rf /sys/firmware/efi/efivars/ as root.
>>
>> If you are dumb enough to do something like that, you almost deserve
>> to spend a couple hundred on a new motherboard.
>
> Or just rm -rf /
> [pedantic]
> of course with newer rm versions one needs to run:
> rm -rf --no-preserve-root /
> or
> rm -rf /* /.*
> [/pedantic]
>
> But in some scenarios this command is normal. E.g. user installs
> Gentoo from some live dvd/flash, makes some mistakes, understands
> that system is broken beyond repair and decides to start over again.
> If there is no need to recreate filesystem itself or partition
> layout, running rm -rf / as above is quite reasonable.
>
> When running this command user expects to kill the data, but not
> the hardware. That is my point. I can't call such action dumb.
>
> Best regards,
> Andrew Savchenko

Point taken.

Although, if the user is in the process of installing Gentoo, efivarfs
is likely to be mounted rw anyway so that the user can install a boot
loader. Having grub-install perform the remount would minimize this
small risk I suppose.