linux-kernel - Re: [PATCH v5 1/2] IMA: Define workqueue for early boot "key" measurements

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Message-Id: <1576846386.5241.13.camel@linux.ibm.com>
Date:   Fri, 20 Dec 2019 07:53:06 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        James.Bottomley@...senPartnership.com,
        linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        mathew.j.martineau@...ux.intel.com, matthewgarrett@...gle.com,
        sashal@...nel.org, jamorris@...ux.microsoft.com,
        linux-kernel@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH v5 1/2] IMA: Define workqueue for early boot "key"
 measurements

On Thu, 2019-12-19 at 08:55 -0800, Lakshmi Ramasubramanian wrote:
> 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?

Ok, using test_and_set_bit() and test_bit() only helps, if we can get
rid of the mutex.  I'll queue these patches.

thanks,

Mimi