linux-kernel - Re: Regression from efi: call get_event

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Message-ID: <CA+zpnLebtbjbA-Jg+RvMOqwDE5R--9V3hTwMk95Br4vM1LgBjQ@mail.gmail.com>
Date:   Fri, 09 Mar 2018 10:43:50 +0000
From:   Thiebaud Weksteen <tweek@...gle.com>
To:     Jeremy Cline <jeremy@...ine.org>
Cc:     hdegoede@...hat.com, Javier Martinez Canillas <javierm@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: Regression from efi: call get_event_log before ExitBootServices

On Fri, Mar 9, 2018 at 10:29 AM Hans de Goede <hdegoede@...hat.com> wrote:

> Hi,

> On 08-03-18 18:26, Jeremy Cline wrote:
> > On 03/08/2018 11:50 AM, Hans de Goede wrote:
> >> <somehow this part of the thread was missing some email addresses, I've
> >> added these now>
> >>
> >> Hi,
> >>
> >> On 07-03-18 12:34, Javier Martinez Canillas wrote:
> >
> > <snip>
> >
> >>> Are you also able to read the TPM event logs?
> >>>
> >>> $ hexdump /sys/kernel/security/tpm0/binary_bios_measurements
> >>
> >> Yes for me that outputs a lot of hex :)
> >
> > For me, /sys/kernel/security/tmp0 doesn't exist on 4.15.6 or 4.16 with
> > the patch reverted.

> Hmm, have you re-enabled the TPM in the BIOS?

> >>> The UEFI firmware does some measurements and so does shim. So you
should
> >>> have some event logs. What version of shim are you using? And also
would
> >>> be good to know if it's the same shim version that Jeremy is using.
> >>
> >> That is a very good question, I'm using: shim-ia32-13-0.7.x86_64,
which is
> >> the last version for F27 AFAICT.
> >
> > All my tablet has installed is shim-0.8-10.x86_64, no shim-ia32.

> Yes my bad, although if the kernel changes break booting on systems
> without the shim that is still good to know and something which
> we probably ought to fix.

> >> But Jeremy's tablet might very well be not using the shim at all, as
> >> I manually installed Fedora 25 on the tablet he now has, before Fedora
> >> supported
> >> machines with 32 bit EFI. I then later did a "dnf distro-sync" to
> >> Fedora-27.
> >>
> >> Jeremy might also very well still be booting using a grub binary I
build
> >> manually back then, without any shim being involved.
> >>
> >> Jeremy what does efibootmgr -v output on your device ?
> >
> > # efibootmgr -v
> > BootCurrent: 0003
> > Timeout: 4 seconds
> > BootOrder: 0003,0000,0001,2001,2002,2003
> > Boot0000* Android X64 OS
> >
HD(1,GPT,215e6cf3-e97d-4735-9c4e-7338c8f5a645,0x800,0x32000)/File(\EFI\BOOT\bootx64.efi)RC
> > Boot0001* Internal EFI Shell
> >
FvVol(a881d567-6cb0-4eee-8435-2e72d33e45b5)/FvFile(c57ad6b7-0515-40a8-9d21-551652854e37)RCM&".
> > Boot0003* Fedora
> >
HD(1,GPT,215e6cf3-e97d-4735-9c4e-7338c8f5a645,0x800,0x32000)/File(\EFI\fedora\grubx64.efi)
> > Boot2001* EFI USB Device      RC
> > Boot2002* EFI DVD/CDROM       RC
> > Boot2003* EFI Network RC
> > Boot8087* Udm
> >
FvVol(a881d567-6cb0-4eee-8435-2e72d33e45b5)/FvFile(9a9ab4c1-ee1b-488b-b300-24544a7bd418)
> >
> > I think you're right about it using the old grub binary. I'm
> > embarrassingly unfamiliar with both UEFI and grub, but I'm guessing you
> > set the location of grub.cfg at compile time? When I boot
> > \EFI\fedora\grubx64.efi, it's pulling the grub.cfg from
> > \EFI\redhat\grub.cfg.

> Ah yes, so I did not build my own grub I took one from RHEL as that had
> 32 bit UEFI support before Fedora got it and as I was lazy I copied the
> 32 bit binary over the 64 bit one, so don't let the filename fool you.

> What you could do is install grub2-efi-ia32 from the Fedora 27 repos
> and then use efibootmgr to add an entry pointing to
\EFI\fedora\grubia32.efi
> note that one will look at \EFI\fedora\grub.cfg .

> Then see if the problem persists. A second step would be to also install
> shim-ia32 and point to that...

Thanks a lot for trying out the patch!

Please don't modify your install at this stage, I think we are hitting a
firmware bug and that would be awesome if we can fix how we are handling it.
So, if we reach that stage in the function it could either be that:
* The allocation did not succeed, somehow, but the firmware still returned
EFI_SUCCEED.
* The size requested is incorrect (I'm thinking something like a 1G of
log). This would be due to either a miscalculation of log_size (possible)
or; the returned values of GetEventLog are not correct.
I'm sending a patch to add checks for these. Could you please apply and
retest?
Again, thanks for helping debugging this.


> Regards,

> Hans