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From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
	James.Bottomley@HansenPartnership.com,
	linux-integrity@vger.kernel.org
Cc: eric.snowberg@oracle.com, dhowells@redhat.com,
	mathew.j.martineau@linux.intel.com, matthewgarrett@google.com,
	sashal@kernel.org, jamorris@linux.microsoft.com,
	linux-kernel@vger.kernel.org, keyrings@vger.kernel.org
Subject: Re: [PATCH v5 1/2] IMA: Define workqueue for early boot "key" measurements
Date: Thu, 19 Dec 2019 16:55:38 +0000	[thread overview]
Message-ID: <503845c9-beeb-b520-ec3f-af5fa7d2b91f@linux.microsoft.com> (raw)
In-Reply-To: <1576761104.4579.426.camel@linux.ibm.com>

On 12/19/19 5:11 AM, Mimi Zohar wrote:

> 
> Getting rid of the temporary list is definitely a big improvement.  As
> James suggested, using test_and_set_bit() and test_bit() would improve
> this code even more.  I think, James correct me if I'm wrong, you
> would be able to get rid of both the mutex and "process".
> 
> Mimi

I am not sure if the mutex can be removed.

In ima_queue_key() we need to test the flag and add the key to the list 
as an atomic operation:

  if (!test_bit())
     insert_key_to_list

Suppose the if condition is true, but before we could insert the key to 
the list, ima_process_queued_keys() runs and processes queued keys we'll 
add the key to the list and never process it.

Is there an API in the kernel to test and add an entry to a list 
atomically?

thanks,
  -lakshmi

WARNING: multiple messages have this Message-ID (diff)
From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
	James.Bottomley@HansenPartnership.com,
	linux-integrity@vger.kernel.org
Cc: eric.snowberg@oracle.com, dhowells@redhat.com,
	mathew.j.martineau@linux.intel.com, matthewgarrett@google.com,
	sashal@kernel.org, jamorris@linux.microsoft.com,
	linux-kernel@vger.kernel.org, keyrings@vger.kernel.org
Subject: Re: [PATCH v5 1/2] IMA: Define workqueue for early boot "key" measurements
Date: Thu, 19 Dec 2019 08:55:38 -0800	[thread overview]
Message-ID: <503845c9-beeb-b520-ec3f-af5fa7d2b91f@linux.microsoft.com> (raw)
In-Reply-To: <1576761104.4579.426.camel@linux.ibm.com>

On 12/19/19 5:11 AM, Mimi Zohar wrote:

> 
> Getting rid of the temporary list is definitely a big improvement.  As
> James suggested, using test_and_set_bit() and test_bit() would improve
> this code even more.  I think, James correct me if I'm wrong, you
> would be able to get rid of both the mutex and "process".
> 
> Mimi

I am not sure if the mutex can be removed.

In ima_queue_key() we need to test the flag and add the key to the list 
as an atomic operation:

  if (!test_bit())
     insert_key_to_list

Suppose the if condition is true, but before we could insert the key to 
the list, ima_process_queued_keys() runs and processes queued keys we'll 
add the key to the list and never process it.

Is there an API in the kernel to test and add an entry to a list 
atomically?

thanks,
  -lakshmi


  reply	other threads:[~2019-12-19 16:55 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 16:44 [PATCH v5 0/2] IMA: Deferred measurement of keys Lakshmi Ramasubramanian
2019-12-18 16:44 ` Lakshmi Ramasubramanian
2019-12-18 16:44 ` [PATCH v5 1/2] IMA: Define workqueue for early boot "key" measurements Lakshmi Ramasubramanian
2019-12-18 16:44   ` Lakshmi Ramasubramanian
2019-12-19 13:11   ` Mimi Zohar
2019-12-19 13:11     ` Mimi Zohar
2019-12-19 16:55     ` Lakshmi Ramasubramanian [this message]
2019-12-19 16:55       ` Lakshmi Ramasubramanian
2019-12-20 12:53       ` Mimi Zohar
2019-12-20 12:53         ` Mimi Zohar
2019-12-18 16:44 ` [PATCH v5 2/2] IMA: Call workqueue functions to measure queued keys Lakshmi Ramasubramanian
2019-12-18 16:44   ` Lakshmi Ramasubramanian
2019-12-20 19:01 ` [PATCH v5 0/2] IMA: Deferred measurement of keys Mimi Zohar
2019-12-20 19:01   ` Mimi Zohar
2019-12-20 19:25   ` Lakshmi Ramasubramanian
2019-12-20 19:25     ` Lakshmi Ramasubramanian
2019-12-20 19:36     ` Mimi Zohar
2019-12-20 19:36       ` Mimi Zohar
2019-12-20 20:50       ` Lakshmi Ramasubramanian
2019-12-20 20:50         ` Lakshmi Ramasubramanian

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