Re: [PATCH] tpm: vtpm_proxy: Do not access host's event log

From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
To: Stefan Berger
	<stefanb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Cc: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: [PATCH] tpm: vtpm_proxy: Do not access host's event log
Date: Wed, 16 Nov 2016 13:07:59 -0700	[thread overview]
Message-ID: <20161116200759.GA19593@obsidianresearch.com> (raw)
In-Reply-To: <65f392b6-5141-c726-dacb-a1649ea215de-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>

On Wed, Nov 16, 2016 at 12:07:23PM -0500, Stefan Berger wrote:
> The culprit seems to be 'tpm: fix the missing .owner in
> tpm_bios_measurements_ops'

That is unlikely, it is probably the patch before which calls read_log
unconditionally now. That suggests the crashing is a little random..

tpm_read_log_acpi should check if the chip has a acpi_dev_handle
before running, but it also shouldn't crash - so there are two bugs
here I guess.. Please do that instead of the checking the virual flag.

Jarkko, you know acpi better, we switched ppi to search starting from
the acpi_dev_handle for its data - can we do the same for event log?

> The crash looks like this:

> [  173.608722]  [<ffffffff8140ca11>] dump_stack+0x63/0x82
> [  173.608722]  [<ffffffff8106b99f>] iounmap.part.1+0x7f/0x90
> [  173.608722]  [<ffffffff8106b9dc>] iounmap+0x2c/0x30
> [  173.608722]  [<ffffffff81496c75>] acpi_os_map_cleanup.part.10+0x31/0x3e
> [  173.608722]  [<ffffffff8179629c>] acpi_os_unmap_iomem+0xcb/0xd2
> [  173.608722]  [<ffffffffa00e1b28>] read_log+0xc8/0x19e [tpm]

This seems really strange ACPI should not crash like this - yes it
will wrongly read the log for the system into the vtpm, but that
*should* work.

Are you doing anything special with this test like high parallism or
something?  Any chance you can look at little more? The tpm code looks
OK to me, the map and unmap are properly paired - but the bad address
from the iounmap suggests the refcounting in acpi is not working or
something along those lines?

Jason

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