linux-kernel - Re: [RFC PATCH v2 1/2] tpm, tpm_tis: Introduce TPM_IOC_SET

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Message-ID: <CAMj1kXExMWBAx7geuU8Uwp9CQLpJyTgYmWUw2CtKd3xT8mMFsg@mail.gmail.com>
Date: Sat, 2 Nov 2024 11:52:03 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: Jonathan Corbet <corbet@....net>, Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>, 
	James.Bottomley@...senpartnership.com, andrew.cooper3@...rix.com, 
	baolu.lu@...ux.intel.com, bp@...en8.de, dave.hansen@...ux.intel.com, 
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	ebiederm@...ssion.com, herbert@...dor.apana.org.au, hpa@...or.com, 
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	kexec@...ts.infradead.org, linux-crypto@...r.kernel.org, 
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	nivedita@...m.mit.edu, ross.philipson@...cle.com, tglx@...utronix.de, 
	trenchboot-devel@...glegroups.com, x86@...nel.org
Subject: Re: [RFC PATCH v2 1/2] tpm, tpm_tis: Introduce TPM_IOC_SET_LOCALITY

On Sat, 2 Nov 2024 at 11:38, Jarkko Sakkinen <jarkko@...nel.org> wrote:
>
> On Sat Nov 2, 2024 at 11:02 AM EET, Ard Biesheuvel wrote:
> > Same for the ioctl() [as well as the read-write sysfs node]: looking
> > at the code (patch 19/20) it doesn't seem like user space needs to be
> > able to modify this at all, at least not for the patch set as
> > presented. So for now, can we just stick with making the sysfs node
> > read-only?
>
> Short answer: I have no idea. I would not mind that but neither
> the commit message for TPM give a clue on this. Actually, I *do
> not care* if it is RO and RW but I'm neither good at guessing
> random shit.
>

You were cc'ed on the rest of the series, no?

Shall we clarify this first, before proposing patches that introduce
new ioctls() and kernel command line parameters to a security
sensitive subsystem?

My reading of 19/20 is that the secure launch module sets the default
locality, and given that it can be built as a module, setting the
default locality needs to be exported to modules (but as I indicated,
this should probably be in a TPM internal module namespace)

If setting the default locality from user space is a requirement down
the road, we can discuss it then. For now, let's not go off into the
weeds and derail this series even more.