linux-kernel - RE: [PATCH 0/2] efivars: reading variables can generate SMIs

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F7B37942B@ORSMSX110.amr.corp.intel.com>
Date:   Fri, 16 Feb 2018 21:09:30 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Joe Konno <joe.konno@...ux.intel.com>,
        "Matthew Garrett" <mjg59@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>
CC:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Jeremy Kerr <jk@...abs.org>, Andi Kleen <ak@...ux.intel.com>,
        Benjamin Drung <benjamin.drung@...fitbricks.com>,
        Peter Jones <pjones@...hat.com>
Subject: RE: [PATCH 0/2] efivars: reading variables can generate SMIs

> That said, I'm not sure how many non-root users run the toolkit to
> extract their EFI certificates or check on the secure boot status of
> the system, but I suspect it might be non-zero: I can see the tinfoil
> hat people wanting at least to check the secure boot status when they
> log in.

Another fix option might be to rate limit EFI calls for non-root users (on X86
since only we have the SMI problem). That would:

1) Avoid using memory to cache all the variables
2) Catch any other places where non-root users can call EFI

-Tony