linux-kernel - Re: [PATCH v2] x86/efi: Add additional efi tables for unencrypted mapping checks

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Message-ID: <b2374776-6499-0b99-9df0-b17a4d84b0e4@amd.com>
Date:   Tue, 25 Feb 2020 13:21:35 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2] x86/efi: Add additional efi tables for unencrypted
 mapping checks

On 2/25/20 12:12 PM, Ard Biesheuvel wrote:
> On Tue, 25 Feb 2020 at 19:10, Tom Lendacky <thomas.lendacky@....com> wrote:
>>
>> On 2/25/20 11:58 AM, Ard Biesheuvel wrote:
>>> On Tue, 25 Feb 2020 at 18:54, Tom Lendacky <thomas.lendacky@....com> wrote:
>>>>
>>>> On 2/25/20 11:45 AM, Ard Biesheuvel wrote:
>>>>> On Tue, 25 Feb 2020 at 18:41, Tom Lendacky <thomas.lendacky@....com> wrote:
>>>>>>
>>>>>> When booting with SME active, EFI tables must be mapped unencrypted since
>>>>>> they were built by UEFI in unencrypted memory. Update the list of tables
>>>>>> to be checked during early_memremap() processing to account for new EFI
>>>>>> tables.
>>>>>>
>>>>>> This fixes a bug where an EFI TPM log table has been created by UEFI, but
>>>>>> it lives in memory that has been marked as usable rather than reserved.
>>>>>>
>>>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>>>>>>
>>>>>> ---
>>>>>> Changes since v1:
>>>>>> - Re-spun against EFI tree
>>>>>
>>>>> Which one? Surely not the one in the link I included?
>>>>
>>>> I did a git clone of
>>>>
>>>>   git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git
>>>>
>>>> and checked out branch next. Not sure what I missed...
>>>>
>>>
>>> Weird. Do you see commit 5d288dbd88606d8f215c7138b10649115d79cadd on
>>> that branch? It removes rng_seed from struct efi, hence my request to
>>> rebase your patch.
>>
>> I had just assumed you wanted a cleaner version and didn't realize that
>> rng_seed was removed from struct efi. My bad for not building.
>>
>>>
>>> IMO, best is to simply drop the 'static' from rng_seed, rename it to
>>> efi_rng_seed, and drop an extern declaration in linux/efi.h so it is
>>> accessible from your code. I'm reluctant to put it back in struct efi.
>>
>> Ok, I'll re-work the patch.
>>
> 
> OK
> 
> Btw if you want the TPM part of the fix to go to -stable, better to
> split them in two (and I'll put a cc:stable on the tpm one)

I had thought about stable, but the fix gets tricky since the two tables
were added at different times (4.16 and 5.3) and the efi_tables array was
moved from drivers/firmware/efi/efi.c to arch/x86/platform/efi/efi.c in 5.4.

I could do the two TPM tables each as their own patch and add an
appropriate Cc: stable # v4.16.x-, etc., if you don't think that's
overkill. The array move shouldn't be too hard to adjust for in stable.
Thoughts?

Thanks,
Tom

>