linux-kernel - Re: [tip:efi/core] 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: <CAKv+Gu_vTHFxpKRu_CxKP-GdNdgdFKr7fi87VkNur0sqGQNVDw@mail.gmail.com>
Date:   Mon, 17 Dec 2018 19:10:58 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "eric.snowberg@...cle.com" <eric.snowberg@...cle.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "arend.vanspriel@...adcom.com" <arend.vanspriel@...adcom.com>,
        "julien.thierry@....com" <julien.thierry@....com>,
        "bhsharma@...hat.com" <bhsharma@...hat.com>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>,
        "joe@...ches.com" <joe@...ches.com>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "natechancellor@...il.com" <natechancellor@...il.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sedat.dilek@...il.com" <sedat.dilek@...il.com>,
        "zhuyifei1999@...il.com" <zhuyifei1999@...il.com>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:efi/core] x86/efi: Unmap EFI boot services code/data regions
 from efi_pgd

On Mon, 17 Dec 2018 at 19:06, Prakhya, Sai Praneeth
<sai.praneeth.prakhya@...el.com> wrote:
>
> > Commit-ID:  08cfb38f3ef49cfd1bba11a00401451606477d80
> > Gitweb:
> > https://git.kernel.org/tip/08cfb38f3ef49cfd1bba11a00401451606477d80
> > Author:     Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> > AuthorDate: Thu, 29 Nov 2018 18:12:24 +0100
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Fri, 30 Nov 2018 09:10:30 +0100
> >
> > x86/efi: Unmap EFI boot services code/data regions from efi_pgd
> >
> > efi_free_boot_services(), as the name suggests, frees EFI boot services
> > code/data regions but forgets to unmap these regions from efi_pgd. This means
> > that any code that's running in efi_pgd address space (e.g:
> > any EFI runtime service) would still be able to access these regions but the
> > contents of these regions would have long been over written by someone else.
> > So, it's important to unmap these regions. Hence, introduce efi_unmap_pages()
> > to unmap these regions from efi_pgd.
> >
> > After unmapping EFI boot services code/data regions, any illegal access by
> > buggy firmware to these regions would result in page fault which will be handled
> > by EFI specific fault handler.
>
> Hi Thomas and Ingo,
>
> I recently noticed that the below commits [1] and [2] are broken when kernel command line
> argument "efi=old_map" is passed. Sorry! I missed to test this condition prior to sending
> these patches to mailing list. I am working on a fix and will send it to mailing list as
> soon as it's ready.
>

Could you elaborate on the problem please?

> Meanwhile, could you please drop these patches before sending pull request to Linus?
>
> [1] Commit 08cfb38f3ef4 ("x86/efi: Unmap EFI boot services code/data regions from efi_pgd")
> [2] Commit 7e0dabd3010d ("x86/mm/pageattr: Introduce helper function to unmap EFI boot services")
>

I'd like to understand what the issue is before we drop anything.