linux-kernel - RE: [PATCH 1/2] x86/efi: Unmap efi boot services code/data regions from efi

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <FFF73D592F13FD46B8700F0A279B802F485D5D88@ORSMSX114.amr.corp.intel.com>
Date:   Mon, 22 Oct 2018 17:35:36 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>
CC:     linux-efi <linux-efi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: RE: [PATCH 1/2] x86/efi: Unmap efi boot services code/data regions
 from efi_pgd

> > The one bit that is odd is the cpa->pfn field - for unmapped pages
> > that's totally uninteresting and I'm wondering whether setting it to 0
> > wouldn't be better.
> >
> > Does the CPU _ever_ look look at the PFN if the page is
> > !_PAGE_PRESENT, for example speculatively? If yes then what is the
> > recommended value for the pfn - zero perhaps?
> >
> 
> This is L1TF, right?  Isn't all ones the recommended value?
> 
> I would love to see EFI start treating its mm just like any other mm at some
> point, though.  That is, it should not modify any mappings in the kernel range,
> and it could use the regular mm modification APIs for the user range.  But maybe
> this is a pipe dream.

Sounds good to me. I have some more fixes for EFI code and as soon as they are done, 
I will start looking into this.

Regards,
Sai