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From: Peter Huewe <peterhuewe-Mmb7MZpHnFY@public.gmane.org>
To: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	"Michal Suchánek" <msuchanek-l3A5Bk7waGM@public.gmane.org>,
	"Jarkko Sakkinen"
	<jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH RESEND 3/3] tpm-chip: Export TPM device to user space even when startup failed
Date: Tue, 29 Aug 2017 15:53:17 +0200	[thread overview]
Message-ID: <E1DD9935-818F-456B-98B3-2103A6799E27@gmx.de> (raw)
In-Reply-To: <20170829151739.315ae581-6hIufAJW0g4CVLCxKZUutA@public.gmane.org>

Thabks Michal!

Am 29. August 2017 15:17:39 MESZ schrieb "Michal Suchánek" <msuchanek@suse.de>:
>Hello,
>
>On Tue, 29 Aug 2017 15:55:09 +0300
>Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote:
>
>> On Mon, Aug 28, 2017 at 05:15:58PM +0000,
>> Alexander.Steffen@infineon.com wrote:
>> > But is that just because nobody bothered to implement the necessary
>> > logic or for some other reason?  
>> 
>> We do not want user space to access broken hardware. It's a huge risk
>> for system stability and potentially could be used for evil purposes.
>> 
>> This is not going to mainline as it is not suitable for general
>> consumption. You must use a patched kernel if you want this.
>> 
>> /Jarkko
>> 
>
>It has been pointed out that userspace applications that use direct IO
>access exist for the purpose. So using a kernel driver is an
>improvement over that if the interface is otherwise sane.
+1

>
>What do you expect is the potential for instability or evil use?
>
>With a kernel driver arbitrating the bus access as it would in any
>other case I do not see much potential for instability. 

Exactly.
 

>If there are
>cases when the arbitration fails they can surely be more likely
>triggered in cases other than userspace sending arbitrary requests to a
>device which is in a state the kernel does not support but otherwise
>responsive.

Its the same as with every other device - as long as it communicates like a tpm, talks like a tpm, behaves like a tpm - it's a tpm. 
Even if the kernel does not recognize the tpm's internal state.


>If you really think that accessing a device that is in unsupported
>state at boot (as opposed to getting unto unsupported state during
>device operation after boot) is a real problem it can be selectable as
>compile time option so people who do not want the code do not get it.

I would more favor a module option, 
but honestly I don't see a reason to not pull this code in, as it is.
Maybe mark the kernel as tainted if you think it is an issue.

Adding this as a out of tree patch is far from userfriendly.
If there is a chance to debug and fix a "unknown" state using the kernel as the communication layer, I would like to use this way.


Peter

>
>Thanks
>
>Michal
>
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  parent reply	other threads:[~2017-08-29 13:53 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-24  8:37 [PATCH RESEND 0/3] Export broken TPMs to user space Alexander Steffen
     [not found] ` <20170824083714.10016-1-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org>
2017-08-24  8:37   ` [PATCH RESEND 1/3] tpm-chip: Move idr_replace calls to appropriate places Alexander Steffen
2017-08-25 17:25     ` Jarkko Sakkinen
     [not found]       ` <20170825172546.f4bl2wh7tgbyjx2n-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-28 17:18         ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-24  8:37   ` [PATCH RESEND 2/3] tpm-chip: Return TPM error codes from auto_startup functions Alexander Steffen
     [not found]     ` <20170824083714.10016-3-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org>
2017-08-25 17:06       ` Jarkko Sakkinen
     [not found]         ` <20170825170607.wfnr5y5zres2n42r-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-29 12:11           ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-24  8:37   ` [PATCH RESEND 3/3] tpm-chip: Export TPM device to user space even when startup failed Alexander Steffen
2017-08-25 17:20     ` Jarkko Sakkinen
     [not found]       ` <20170825172021.lw3ycxqw63ubrcm2-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-28 17:15         ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-29 12:55           ` Jarkko Sakkinen
2017-08-29 13:17             ` [tpmdd-devel] " Michal Suchánek
     [not found]               ` <20170829151739.315ae581-6hIufAJW0g4CVLCxKZUutA@public.gmane.org>
2017-08-29 13:53                 ` Peter Huewe [this message]
2017-08-30 10:26                   ` Jarkko Sakkinen
2017-08-30 10:15                 ` Jarkko Sakkinen
2017-08-30 10:20                   ` [tpmdd-devel] " Jarkko Sakkinen
2017-08-30 10:34                     ` Michal Suchánek
2017-08-30 11:07                       ` Jarkko Sakkinen
2017-08-31 16:18                         ` Alexander.Steffen
2017-09-02 10:20                           ` Jarkko Sakkinen
     [not found]                   ` <20170830101510.rlkh2p3zecfsrhgl-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-30 10:41                     ` Peter Huewe
2017-08-30 11:10                       ` [tpmdd-devel] " Jarkko Sakkinen
2017-08-31 16:26                         ` Alexander.Steffen
2017-09-02 10:24                           ` Jarkko Sakkinen

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