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

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Message-ID: <a259a629-def7-b538-2a54-8ca6bfbe772a@huawei.com>
Date:   Mon, 19 Nov 2018 09:14:00 +0100
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     <zohar@...ux.ibm.com>, <david.safford@...com>,
        <monty.wiseman@...com>, <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v5 6/7] tpm: ensure that the output of PCR read contains
 the correct digest size

On 11/18/2018 8:32 AM, Jarkko Sakkinen wrote:
> On Fri, Nov 16, 2018 at 05:06:48PM +0100, Roberto Sassu wrote:
>> On 11/16/2018 2:41 PM, Jarkko Sakkinen wrote:
>>> On Wed, Nov 14, 2018 at 04:31:07PM +0100, Roberto Sassu wrote:
>>>> 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@...wei.com>
>>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>>>> Cc: stable@...r.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.

Roberto


> /Jarkko
> 

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