linux-kernel - Re: Fwd: Re: [tpmdd-devel] [PATCH v9 2/2] tpm: add securityfs support,for TPM 2.0 firmware event log

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Message-Id: <58923635.8060004@linux.vnet.ibm.com>
Date:   Thu, 2 Feb 2017 00:55:41 +0530
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Kenneth Goldman <kgoldman@...ibm.com>,
        "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org
Subject: Re: Fwd: Re: [tpmdd-devel] [PATCH v9 2/2] tpm: add securityfs
 support,for TPM 2.0 firmware event log



On 02/01/2017 08:24 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 01, 2017 at 04:48:37PM +0200, Jarkko Sakkinen wrote:
>> On Tue, Jan 31, 2017 at 10:50:06PM +0200, Jarkko Sakkinen wrote:
>>> On Wed, Feb 01, 2017 at 12:14:12AM +0530, Nayna wrote:
>>>>> I already sent my pull request to 4.11 and even today I found something
>>>>> fishy. You declared a function local array by using a variable in "tpm:
>>>>> enhance TPM 2.0 PCR extend to support multiple banks" (max_active_banks
>>>>> or something). And the event log patches have just passed the review.
>>>>
>>>> Yes. I have checked using clang and it has passed the clang.. and I also
>>>> verified there were no complains during build.
>>>
>>> What we can deduce from that is that they didn't expose the issue in
>>> question.
>>>
>>> I found this by running sparse with make C=2 M=drives/char/tpm
>>>
>>>> What type of problem do you see ?
>>>
>>> It is disallowed to do stack allocation in the kernel code even if C
>>> standard would allow it. Stack is scarce resource so you need to know
>>> its usage at compile time.
>>>
>>> In this case you actually know the allocation because the value is not
>>> changed during the course of the function but it is still bad. Probably
>>> compiler will optimize it out. Still it is not a good practice.
>>>
>>>> Also, to understand, this is related to multi-bank patchset. I mean how does
>>>> it affect for event log patchset ?
>>>
>>> Well in both cases these have landed fairly late but I asked from James
>>> whether I'll have to postpone these to 4.12.
>>>
>>> Usually when I've sent my release pull request I do not want to make any
>>> radical changes to the codebase because they always require extra QA and
>>> thus take extra time.
>>
>> rc = tpm_transmit_cmd(chip, buf.data, tpm_buf_length(&buf), 0, 0,
>> 		      "attempting extend a PCR value");
>>
>> This should be
>>
>> rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0, 0,
>> 		      "attempting extend a PCR value");
>>
>> The second parameter is the size of the buffer, not length of the input
>> data.
>>
>> /Jarkko
>
> As a sanity check can you test these commits and see if they still
> work for you as I've done now some updates to them? Thanks.

Thanks Jarkko, yes I tested for both multi-bank patches and event log.
Its working fine.

Thanks & Regards,
    - Nayna

>
> /Jarkko
>