Re: [PATCH] x86/microcode/AMD: check microcode file sanity before loading it

Borislav Petkov
2018-03-10T16:47:13Z

On Sat, Mar 10, 2018 at 05:16:40PM +0100, Maciej S. Szmigiero wrote:
> To make sure that it is clear what this patch is about:

I know what you're trying to do but it seems you don't want to listen.
So let me try one last time to clear your confusion.

> It *isn't* about verifying the actual microcode update, that is, the
> blob that gets sent to the CPU as the new microcode.
> Such verification is (hopefully) done by the CPU itself.

Yes, it is done by the CPU. Microcode is encrypted.

> There is no container file at all for family 17h (Zen) so
> distributions like OpenSUSE that include this file must have gotten it
> from some other source

Or maybe they've gotten it from AMD directly. Don't you think that
getting microcode from the CPU vendor directly is the logical thing?

> That's why to get things like IBPB it is sometimes necessary to use
> a newer microcode version than included in linux-firmware, sourced for
> example from a BIOS update.

linux-firmware will get F17h microcode soon.

> Since BIOS updates contain only actual (raw) microcode updates one
> has to place it in a microcode container file so this driver can parse
> it.
>
> As far I know there is no tool to automate this work so one has to
> manually tweak the container metadata.

Let me get this straight: am I reading this correctly that you've tried
to carve out the F17h microcode from a BIOS update blob and you're
trying to load that?!?

If so, you could've simply taken a distro microcode package and used
F17h microcode from there - they are all the same.

--
Regards/Gruss,
Boris.

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