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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 16 Feb 2018 11:18:12 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Joe Konno <joe.konno@...ux.intel.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.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>,
        Tony Luck <tony.luck@...el.com>,
        Benjamin Drung <benjamin.drung@...fitbricks.com>,
        Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH 0/2] efivars: reading variables can generate SMIs

On 16 February 2018 at 11:08, Borislav Petkov <bp@...en8.de> wrote:
> On Fri, Feb 16, 2018 at 10:58:47AM +0000, Ard Biesheuvel wrote:
>> By your own reasoning above, that's a no-no as well.
>
> I'm sure we can come up with some emulation - the same way we did the
> BIOS emulation.
>
>> But thanks for your input. Anyone else got something constructive to contribute?
>
> The not-breaking userspace is constructive contribution. The last
> paragraph is my usual rant.
>

Fair enough. And I am not disagreeing with you either.

So question to Joe: is it well defined which variables may exhibit
this behavior? Given that UEFI variables are GUID scoped, would
whitelisting certain GUIDs (the ones userland currently relies on to
be readable my non-privileged users) and making everything else
user-only solve this problem as well?