linux-kernel - Re: [PATCH RFC 4/4] tpm: add the infrastructure for TPM space for TPM 2.0

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Message-ID: <20170104124354.wga6lngg4gkpeefv@intel.com>
Date:   Wed, 4 Jan 2017 14:43:54 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 4/4] tpm: add the infrastructure for TPM space for
 TPM 2.0

On Tue, Jan 03, 2017 at 11:46:27AM -0700, Jason Gunthorpe wrote:
> On Tue, Jan 03, 2017 at 02:37:30AM +0200, Jarkko Sakkinen wrote:
> > On Mon, Jan 02, 2017 at 02:09:53PM -0700, Jason Gunthorpe wrote:
> > > On Mon, Jan 02, 2017 at 03:22:10PM +0200, Jarkko Sakkinen wrote:
> > > > Added a ioctl for creating a TPM space. The space is isolated from the
> > > > other users of the TPM. Only a process holding the file with the handle
> > > > can access the objects and only objects that are created through that
> > > > file handle can be accessed.
> > > 
> > > I don't understand this comment. /dev/tpmX is forced to be
> > > single-process-open, so how can there ever be more than 1 FD for it?
> > > 
> > > Since the space is tied to that single fd these patches just create a
> > > way for the single user-space process to auto-cleanup if it crashes?
> > > 
> > > Is that the entire intent of this design? I guess it is OK as a
> > > stepping point..
> > 
> > is_open is cleared in tpm_ioc_new_space.
> 
> That is no good, it is racy if the intention is to use multiple
> clients, and any single client that doesn't support the new API blocks
> all access.

Luckily this will be implicitly fixed with a separate device file 
in the non-RFC patch set :-)

> Jason

/Jarkko