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

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Message-ID: <CA+zpnLdmg30Beg+uUJNgBQ5gbjXuJ0uVhyzCgf6m7xbx2yARBg@mail.gmail.com>
Date:   Sat, 10 Mar 2018 10:45:20 +0000
From:   Thiebaud Weksteen <tweek@...gle.com>
To:     Jeremy Cline <jeremy@...ine.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.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 5:54 PM Jeremy Cline <jeremy@...ine.org> wrote:

> On Fri, Mar 09, 2018 at 10:43:50AM +0000, Thiebaud Weksteen wrote:
> > 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.

> No problem, thanks for the help :)

> With the new patch:

> Locating the TCG2Protocol
> Calling GetEventLog on TCG2Protocol
> Log returned
> log_location is not empty
> log_size != 0
> log_size < 1M
> Allocating memory for storing the logs
> Returned from memory allocation
> Copying log to new location

> And then it hangs. I added a couple more print statements:

> diff --git a/drivers/firmware/efi/libstub/tpm.c
b/drivers/firmware/efi/libstub/tpm.c
> index ee3fac109078..1ab5638bc50e 100644
> --- a/drivers/firmware/efi/libstub/tpm.c
> +++ b/drivers/firmware/efi/libstub/tpm.c
> @@ -148,8 +148,11 @@ void
efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>          efi_printk(sys_table_arg, "Copying log to new location\n");

>          memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
> +       efi_printk(sys_table_arg, "Successfully memset log_tbl to 0\n");
>          log_tbl->size = log_size;
> +       efi_printk(sys_table_arg, "Set log_tbl->size\n");
>          log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
> +       efi_printk(sys_table_arg, "Set log_tbl-version\n");
>          memcpy(log_tbl->log, (void *) first_entry_addr, log_size);

>          efi_printk(sys_table_arg, "Installing the log into the
configuration table\n");

> and it's hanging at "memset(log_tbl, 0, sizeof(*log_tbl) + log_size);"

Thanks. Well, it looks like the memory that is supposedly allocated is not
usable. I'm thinking this is a firmware bug.
Ard, would you agree on this assumption? Thoughts on how to proceed?

Thanks


> Regards,
> Jeremy