Re: [PATCH] tpm: fix a race condition tpm2_unseal_trusted()

From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Peter Huewe <peterhuewe@gmx.de>,
	linux-security-module@vger.kernel.org,
	Marcel Selhorst <tpmdd@selhorst.net>,
	"moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@lists.sourceforge.net>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tpm: fix a race condition tpm2_unseal_trusted()
Date: Wed, 20 Jul 2016 10:48:18 -0600	[thread overview]
Message-ID: <20160720164818.GA21460@obsidianresearch.com> (raw)
In-Reply-To: <1468973792-17598-1-git-send-email-jarkko.sakkinen@linux.intel.com>

On Wed, Jul 20, 2016 at 03:16:32AM +0300, Jarkko Sakkinen wrote:
> Unseal and load operations should be done as an atomic unit. This
> commit fixes the issue by moving TPM mutex handling to tpm_try_get_ops()
> and tpm_put_ops(), which is probably more logical place for it anyway.

No..

'get_ops' is to be used to hold a persisent kref to a single tpm. It
cannot block other tpm access.

Eg a upper protocol might get_ops to for a long period to ensure it
consistently talks to the same TPM in a multi-tpm system.

We need something else to solve whatever you are concerned with
here..

Jason