Thread (38 messages) 38 messages, 3 authors, 2018-12-03

Re: [PATCH v5 6/7] tpm: ensure that the output of PCR read contains the correct digest size

From: Jarkko Sakkinen <hidden>
Date: 2018-11-19 14:34:03
Also in: linux-integrity, lkml, stable

On Mon, Nov 19, 2018 at 09:14:00AM +0100, Roberto Sassu wrote:
On 11/18/2018 8:32 AM, Jarkko Sakkinen wrote:
quoted
On Fri, Nov 16, 2018 at 05:06:48PM +0100, Roberto Sassu wrote:
quoted
On 11/16/2018 2:41 PM, Jarkko Sakkinen wrote:
quoted
On Wed, Nov 14, 2018 at 04:31:07PM +0100, Roberto Sassu wrote:
quoted
This patch protects against data corruption that could happen in the bus,
by checking that that the digest size returned by the TPM during a PCR read
matches the size of the algorithm passed to tpm2_pcr_read().

This check is performed after information about the PCR banks has been
retrieved.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <redacted>
Cc: stable@vger.kernel.org
Missing fixes tag.
Before this patch set, tpm2_pcr_extend() always copied 20 bytes from the
output sent by the TPM.

Roberto
Aah, right, of course. Well the patch set is ATM somewhat broken because
this would require a fixes tag that points to a patch insdie the patch
set.

Probably good way to fix the issue is to just merge this with the
earlier commit.
Unfortunately, it is not possible. The exact digest size has been
introduced with patch 5/7.
I put this in simple terms: if I merge 5/7 the driver will be broken.
Any commit in the patch set should not leave the tree in broken state.

That implies that 5/7 and 6/7 cannot be separate commits.

/Jarkko
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