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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Stefan Berger <stefanb@linux.vnet.ibm.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
	linux-integrity@vger.kernel.org, jarkko.sakkinen@linux.intel.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] ima: Use tpm_chip_find() and access TPM functions using it
Date: Thu, 21 Jun 2018 21:25:36 -0600	[thread overview]
Message-ID: <20180622032536.GB19151@ziepe.ca> (raw)
In-Reply-To: <f4af7347-a9dd-1683-5c2c-faeb45750e2e@linux.vnet.ibm.com>

On Thu, Jun 21, 2018 at 04:59:55PM -0400, Stefan Berger wrote:
> On 06/21/2018 04:53 PM, Mimi Zohar wrote:
> >On Wed, 2018-06-20 at 16:42 -0400, Stefan Berger wrote:
> >>Rather than accessing the TPM functions using a NULL pointer, which
> >>causes a lookup for a suitable chip every time, get a hold of a tpm_chip
> >>and access the TPM functions using this chip. We call the tpm_chip
> >>ima_tpm_chip and protect it, once initialization is done, using a
> >>rw_semaphore called ima_tpm_chip_lock.
> >>
> >>Use ima_shutdown to release the tpm_chip.
> >>
> >>Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> >>  security/integrity/ima/ima.h        |  3 +++
> >>  security/integrity/ima/ima_crypto.c | 12 ++++++++++--
> >>  security/integrity/ima/ima_init.c   | 19 ++++++++++++-------
> >>  security/integrity/ima/ima_queue.c  |  7 +++++--
> >>  4 files changed, 30 insertions(+), 11 deletions(-)
> >>
> >>diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> >>index 354bb5716ce3..53a88d578ca5 100644
> >>+++ b/security/integrity/ima/ima.h
> >>@@ -24,6 +24,7 @@
> >>  #include <linux/hash.h>
> >>  #include <linux/tpm.h>
> >>  #include <linux/audit.h>
> >>+#include <linux/rwsem.h>
> >>  #include <crypto/hash_info.h>
> >>
> >>  #include "../integrity.h"
> >>@@ -56,6 +57,8 @@ extern int ima_policy_flag;
> >>  extern int ima_used_chip;
> >>  extern int ima_hash_algo;
> >>  extern int ima_appraise;
> >>+extern struct rw_semaphore ima_tpm_chip_lock;
> >>+extern struct tpm_chip *ima_tpm_chip;
> >
> >ima_add_templatE_entry() synchronizes appending a measurement to the
> >measurement list and extending the TPM by taking a lock.  Do we really
> >need to introduce another lock?
> 
> This lock protects the ima_tpm_chip from going from != NULL to NULL in the
> ima_shutdown function. Basically, a global pointer accessed by concurrent
> threads should be protected if its value can change. However, in this case
> ima_shutdown would be called so late that there shouldn't be concurrency
> anymore. Though, I found it better to protect it. Maybe someone else has an
> opinion?

Why have a shutdown block? There is no harm in holding a kref if the
machine is shutting down.

Jason

  reply	other threads:[~2018-06-22  3:25 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-20 20:42 [PATCH v2 0/4] Have IMA find and use a tpm_chip until system shutdown Stefan Berger
2018-06-20 20:42 ` [PATCH v2 1/4] tpm: Implement tpm_chip_find() and tpm_chip_put() for other subsystems Stefan Berger
2018-06-20 20:50   ` Jason Gunthorpe
2018-06-20 21:13     ` Stefan Berger
2018-06-21 17:13     ` Jarkko Sakkinen
2018-06-21 17:15   ` Jarkko Sakkinen
2018-06-21 17:27     ` Stefan Berger
2018-06-21 17:45     ` Stefan Berger
2018-06-21 17:56       ` Jason Gunthorpe
2018-06-21 18:19         ` Stefan Berger
2018-06-21 19:06           ` Jason Gunthorpe
2018-06-21 20:14             ` Stefan Berger
2018-06-21 20:51               ` Jason Gunthorpe
2018-06-20 20:42 ` [PATCH v2 2/4] ima: Implement ima_shutdown and register it as a reboot_notifier Stefan Berger
2018-06-20 20:42 ` [PATCH v2 3/4] ima: Use tpm_chip_find() and access TPM functions using it Stefan Berger
2018-06-21 20:53   ` Mimi Zohar
2018-06-21 20:59     ` Stefan Berger
2018-06-22  3:25       ` Jason Gunthorpe [this message]
2018-06-22 11:40         ` Stefan Berger
2018-06-22 14:19           ` Jason Gunthorpe
2018-06-20 20:42 ` [PATCH v2 4/4] ima: Get rid of ima_used_chip and use ima_tpm_chip != NULL instead Stefan Berger

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