From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
To: Jarkko Sakkinen <jarkko@kernel.org>,
Lino Sanfilippo <l.sanfilippo@kunbus.com>,
Alexander Steffen <Alexander.Steffen@infineon.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Sasha Levin <sashal@kernel.org>,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Ross Philipson <ross.philipson@oracle.com>,
Kanth Ghatraju <kanth.ghatraju@oracle.com>,
Peter Huewe <peterhuewe@gmx.de>
Subject: Re: [PATCH 1/3] tpm: protect against locality counter underflow
Date: Thu, 22 Feb 2024 20:58:40 -0500 [thread overview]
Message-ID: <88b75c9c-98ab-4474-8112-6a27d11a2fdf@apertussolutions.com> (raw)
In-Reply-To: <CZA9ADCGOTQT.LB5XHZZVTWVH@seitikki>
On 2/20/24 17:23, Jarkko Sakkinen wrote:
> On Tue Feb 20, 2024 at 8:54 PM UTC, Lino Sanfilippo wrote:
>> Hi,
>>
>> On 20.02.24 19:42, Alexander Steffen wrote:
>>> ATTENTION: This e-mail is from an external sender. Please check attachments and links before opening e.g. with mouseover.
>>>
>>>
>>> On 02.02.2024 04:08, Lino Sanfilippo wrote:
>>>> On 01.02.24 23:21, Jarkko Sakkinen wrote:
>>>>
>>>>>
>>>>> On Wed Jan 31, 2024 at 7:08 PM EET, Daniel P. Smith wrote:
>>>>>> Commit 933bfc5ad213 introduced the use of a locality counter to control when a
>>>>>> locality request is allowed to be sent to the TPM. In the commit, the counter
>>>>>> is indiscriminately decremented. Thus creating a situation for an integer
>>>>>> underflow of the counter.
>>>>>
>>>>> What is the sequence of events that leads to this triggering the
>>>>> underflow? This information should be represent in the commit message.
>>>>>
>>>>
>>>> AFAIU this is:
>>>>
>>>> 1. We start with a locality_counter of 0 and then we call tpm_tis_request_locality()
>>>> for the first time, but since a locality is (unexpectedly) already active
>>>> check_locality() and consequently __tpm_tis_request_locality() return "true".
>>>
>>> check_locality() returns true, but __tpm_tis_request_locality() returns
>>> the requested locality. Currently, this is always 0, so the check for
>>> !ret will always correctly indicate success and increment the
>>> locality_count.
>>>
>>
>> Will the TPM TIS CORE ever (have to) request another locality than 0? Maybe the best would
>> be to hardcode TPM_ACCESS(0) and get rid of all the locality parameters that are
>> passed from one function to another.
>
> Usually, or at least use cases I'm aware of, localities are per
> component. E.g. Intel TXT has one and Linux has another.
>
> There's been some proposals in the past here for hypervisor specific
> locality here at LKML they didn't lead to anything.
>
> If you are suggesting of removing "int l" parameter altogether, I
> do support that idea.
>
>> But this is rather code optimization and not really required to fix
>> the reported bug.
>
> Just adding here that I wish we also had a log transcript of bug, which
> is right now missing. The explanation believable enough to move forward
> but I still wish to see a log transcript.
That will be forth coming.
v/r,
dps
next prev parent reply other threads:[~2024-02-23 1:58 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240131170824.6183-1-dpsmith@apertussolutions.com>
2024-01-31 17:08 ` [PATCH 1/3] tpm: protect against locality counter underflow Daniel P. Smith
2024-02-01 22:21 ` Jarkko Sakkinen
2024-02-02 3:08 ` Lino Sanfilippo
2024-02-12 20:05 ` Jarkko Sakkinen
2024-02-19 17:54 ` Daniel P. Smith
2024-02-20 18:42 ` Alexander Steffen
2024-02-20 19:04 ` Jarkko Sakkinen
2024-02-20 20:54 ` Lino Sanfilippo
2024-02-20 22:23 ` Jarkko Sakkinen
2024-02-20 23:19 ` Lino Sanfilippo
2024-02-21 0:40 ` Jarkko Sakkinen
2024-02-23 1:58 ` Daniel P. Smith [this message]
2024-02-23 12:58 ` Jarkko Sakkinen
2024-02-25 11:23 ` Daniel P. Smith
2024-02-26 9:39 ` Jarkko Sakkinen
2024-02-20 22:26 ` Jarkko Sakkinen
2024-02-20 22:31 ` Jarkko Sakkinen
2024-02-20 23:26 ` Lino Sanfilippo
2024-02-21 0:42 ` Jarkko Sakkinen
2024-02-21 12:37 ` James Bottomley
2024-02-21 19:43 ` Jarkko Sakkinen
2024-02-21 19:45 ` Jarkko Sakkinen
2024-02-22 9:06 ` James Bottomley
2024-02-22 23:49 ` Jarkko Sakkinen
2024-02-23 1:57 ` Daniel P. Smith
2024-02-23 20:40 ` Jarkko Sakkinen
2024-02-23 20:42 ` Jarkko Sakkinen
2024-02-23 1:57 ` Daniel P. Smith
2024-02-23 20:50 ` Jarkko Sakkinen
2024-02-20 22:57 ` ross.philipson
2024-02-20 23:10 ` Jarkko Sakkinen
2024-02-20 23:13 ` Jarkko Sakkinen
2024-02-23 1:56 ` Daniel P. Smith
2024-02-23 20:44 ` Jarkko Sakkinen
2024-02-24 2:34 ` Lino Sanfilippo
2024-02-26 9:38 ` Jarkko Sakkinen
2024-02-23 1:55 ` Daniel P. Smith
2024-02-26 12:43 ` Alexander Steffen
2024-02-24 2:06 ` Lino Sanfilippo
2024-02-23 0:01 ` Jarkko Sakkinen
2024-01-31 17:08 ` [PATCH 2/3] tpm: ensure tpm is in known state at startup Daniel P. Smith
2024-02-01 22:33 ` Jarkko Sakkinen
2024-02-19 19:17 ` Daniel P. Smith
2024-02-19 20:17 ` Jarkko Sakkinen
2024-01-31 17:08 ` [PATCH 3/3] tpm: make locality request return value consistent Daniel P. Smith
2024-02-01 22:49 ` Jarkko Sakkinen
2024-02-19 20:29 ` Daniel P. Smith
2024-02-19 20:45 ` Jarkko Sakkinen
2024-02-20 18:57 ` Alexander Steffen
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