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

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Date:   Mon, 26 Aug 2019 10:44:31 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Peter Jones <pjones@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        Bartosz Szczepanek <bsz@...ihalf.com>,
        Lyude Paul <lyude@...hat.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] efi+tpm: Don't access event->count when it isn't mapped.

On Mon, Aug 26, 2019 at 9:28 AM Jarkko Sakkinen
<jarkko.sakkinen@...ux.intel.com> wrote:
>
> On Mon, Aug 26, 2019 at 11:30:27AM -0400, Peter Jones wrote:
> > 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.
> >
> > 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>

Jarkko, these two should probably go to 5.3 if possible - I
independently had a report of a system hitting this issue last week
(Intel apparently put a surprising amount of data in the event logs on
the NUCs).