Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 11 Apr 2018 15:38:27 -0700 | Subject | Re: [PATCH 01/24] Add the ability to lock down access to the running kernel image |
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On Wed, Apr 11, 2018 at 2:05 PM, Jordan Glover <Golden_Miller83@protonmail.ch> wrote: >> >> If that /dev/mem access prevention was just instead done as an even >> stricter mode of the existing CONFIG_STRICT_DEVMEM, it could just be >> enabled unconditionally. > > CONFIG_DEVMEM=n
It's actually CONFIG_DEVMEM, CONFIG_DEVKMEM and CONFIG_DEVPORT, it's just not obvious from the patch.
But the important part is this part:
>> So I would seriously ask that the distros that have been using these >> patches look at which parts of lockdown they could make unconditional >> (because it doesn't break machines), and which ones need that escape >> clause.
.. because I get the feeling that not a lot of people have actually been testing this, because "turn off secure boot" is such a universal thing when people boot Linux.
So it's really the whole claim that distributions have been running for this for the last five years that I wonder about, and how often people end up being told: "just disable secure boot":.
But if people really don't need DEVMEM/DEVKMEM/DEVPORT, maybe we should just disable them in the default configs, and consider them legacy.
I'm just surprised. I suspect a lot of people end up actually using devmem as a fallback for dmidecode etc. Maybe those people don't boot with EFI secure mode, but if so that just shows that this whole "hardening" is just security theater.
Linus
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