linux-kernel - Re: [PATCH v2 1/2] efi+tpm: Don't access event->count when it isn't mapped.

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Date:   Wed, 25 Sep 2019 09:41:33 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Peter Jones <pjones@...hat.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        stable <stable@...r.kernel.org>, Lyude Paul <lyude@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        Bartosz Szczepanek <bsz@...ihalf.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] efi+tpm: Don't access event->count when it isn't
 mapped.

On Wed Sep 25 19, Jerry Snitselaar wrote:
>On Wed Sep 25 19, Jarkko Sakkinen wrote:
>>On Wed, Sep 25, 2019 at 12:25:05PM +0200, Ard Biesheuvel wrote:
>>>On Wed, 25 Sep 2019 at 12:16, Jarkko Sakkinen
>>><jarkko.sakkinen@...ux.intel.com> wrote:
>>>>
>>>> From: Peter Jones <pjones@...hat.com>
>>>>
>>>> Some machines generate a lot of event log entries.  When we're
>>>> iterating over them, the code removes the old mapping and adds a
>>>> new one, so once we cross the page boundary we're unmapping the page
>>>> with the count on it.  Hilarity ensues.
>>>>
>>>> This patch keeps the info from the header in local variables so we don't
>>>> need to access that page again or keep track of if it's mapped.
>>>>
>>>> Fixes: 44038bc514a2 ("tpm: Abstract crypto agile event size calculations")
>>>> Cc: linux-efi@...r.kernel.org
>>>> Cc: linux-integrity@...r.kernel.org
>>>> Cc: stable@...r.kernel.org
>>>> Signed-off-by: Peter Jones <pjones@...hat.com>
>>>> Tested-by: Lyude Paul <lyude@...hat.com>
>>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>>>> Acked-by: Matthew Garrett <mjg59@...gle.com>
>>>> Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>>>> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>>>
>>>Thanks Jarkko.
>>>
>>>Shall I take these through the EFI tree?
>>
>>Would be great, if you could because I already sent one PR with fixes for
>>v5.4-rc1 yesterday.
>>
>>/Jarkko
>
>My patch collides with this, so I will submit a v3 that applies on top of
>these once I've run a test with all 3 applied on this t480s.

Tested with Peter's patches, and that was the root cause on this 480s.

I think there should still be a check for tbl_size to make sure we
aren't sticking -1 into efi_tpm_final_log_size though, which will be
the case right now if it fails to parse an event.