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From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Stefan Berger <stefanb@linux.vnet.ibm.com>,
	linux-integrity@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"open list:INTEGRITY MEASUREMENT ARCHITECTURE IMA"
	<linux-ima-user@lists.sourceforge.net>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	open list <linux-kernel@vger.kernel.org>,
	linux-security-module@vger.kernel.org,
	"moderated list:TPM DEVICE DRIVER"
	<tpmdd-devel@lists.sourceforge.net>,
	"open list:KEYS-TRUSTED" <keyrings@vger.kernel.org>,
	"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
	<linux-crypto@vger.kernel.org>,
	James Morris <james.l.morris@oracle.com>,
	Matt Mackall <mpm@selenic.c>
Subject: Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from in-kernel API
Date: Tue, 24 Oct 2017 10:02:00 -0700
Message-ID: <CAKdAkRT9sLux6S1qdd=j0nbXSBdnYGG_hvjny=ic0YJLVNnxzA@mail.gmail.com> (raw)
In-Reply-To: <20171024161118.GA348@obsidianresearch.com>

On Tue, Oct 24, 2017 at 9:11 AM, Jason Gunthorpe
<jgunthorpe@obsidianresearch.com> wrote:
> On Tue, Oct 24, 2017 at 09:37:33PM +0530, PrasannaKumar Muralidharan wrote:
>> Hi Jason,
>>
>> On 24 October 2017 at 21:25, Jason Gunthorpe
>> <jgunthorpe@obsidianresearch.com> wrote:
>> > On Tue, Oct 24, 2017 at 09:21:15PM +0530, PrasannaKumar Muralidharan wrote:
>> >
>> >> Please check the RFC [1]. It does use chip id. The rfc has issues and
>> >> has to be fixed but still there could be users of the API.
>> >>
>> >> 1. https://www.spinics.net/lists/linux-crypto/msg28282.html
>> >
>> > That patch isn't safe at all. You need to store a kref to th chip in
>> > the hwrng, not parse a string.
>>
>> The drivers/char/hw_random/tpm-rng.c module does not store the chip
>> reference so I guess the usage is safe.
>
> It is using the default TPM, it is always safe to use the default tpm.

tpm-rng is abomination that should be kicked out as soon as possible.
It wrecks havoc with the power management (TPM chip drivers may go
into suspend state, but tpm_rng does not do any power management and
happily forwards requests to suspended hardware) and may be available
when there is no TPM at all yet (the drivers have not been probed yet,
or have gotten a deferral, etc).

TPM core should register HWRNGs when chips are ready.

Thanks.

-- 
Dmitry

  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-23 12:38 Jarkko Sakkinen
2017-10-23 14:07 ` [tpmdd-devel] " Stefan Berger
2017-10-23 16:31   ` Jason Gunthorpe
2017-10-24 15:44     ` Jarkko Sakkinen
     [not found]       ` <20171024154440.3jeupmus43jcgbbz-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-10-24 15:51         ` PrasannaKumar Muralidharan
2017-10-24 15:55           ` [tpmdd-devel] " Jason Gunthorpe
2017-10-24 16:07             ` PrasannaKumar Muralidharan
2017-10-24 16:11               ` Jason Gunthorpe
2017-10-24 16:14                 ` PrasannaKumar Muralidharan
2017-10-24 17:46                   ` Jason Gunthorpe
2017-10-24 17:56                     ` PrasannaKumar Muralidharan
2017-10-24 17:02                 ` Dmitry Torokhov [this message]
2017-10-24 17:37                   ` Jason Gunthorpe
2017-10-24 17:44                     ` PrasannaKumar Muralidharan
     [not found]                     ` <20171024173757.GA1806-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-10-24 18:04                       ` Dmitry Torokhov
2017-10-24 18:15                   ` [tpmdd-devel] " Jarkko Sakkinen
     [not found]                     ` <20171024181512.iaxtzgxexhki7aqr-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-10-24 18:40                       ` Peter Huewe
2017-10-24 16:23           ` [tpmdd-devel] " Jarkko Sakkinen
2017-10-24 16:35             ` PrasannaKumar Muralidharan
     [not found]               ` <CANc+2y4vtr+kbhC_7Rv=rHA2LgEVBHLFEu+DYYK1UmpU63PCgQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-24 18:22                 ` Jarkko Sakkinen
     [not found]                   ` <20171024182235.d7b3oajc5zcjs57v-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-10-25 14:51                     ` PrasannaKumar Muralidharan
2017-10-25 19:11                       ` [tpmdd-devel] " Jarkko Sakkinen
2017-10-26 16:23                         ` PrasannaKumar Muralidharan
2017-10-24 14:04   ` Jarkko Sakkinen

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