linux-kernel - Re: [PATCH v5 3/4] LSM: Define SELinux function to measure state and policy

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Message-ID: <a66155ea-151d-cfd7-01f0-15ed6f18e26b@linux.microsoft.com>
Date:   Tue, 4 Aug 2020 08:57:02 -0700
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Stephen Smalley <stephen.smalley.work@...il.com>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>, sashal@...nel.org,
        James Morris <jmorris@...ei.org>,
        linux-integrity@...r.kernel.org,
        SElinux list <selinux@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3/4] LSM: Define SELinux function to measure state and
 policy

On 8/4/20 8:29 AM, Stephen Smalley wrote:

>>> Perhaps vmalloc would be better than using kmalloc? If there are 
>>> better options for such large buffer allocation, please let me know.
>>
>> kvmalloc() can be used to select whichever one is most appropriate.
> 
> Other option would be for ima to compute and save the hash(es) of the 
> payload and not the payload itself for later use.  I guess you won't 
> know at that point which hash algorithm is desired?
> 

I think IMA hash algorithm would be known at that point, but IMA policy 
is not loaded yet (which is why I need to queue up the buffer and 
process when policy is loaded).

I tried vmalloc and tested it with upto 16MB buffer (just made up a 
SELinux policy buffer of size 16MB) - that works fine.

I will try kvmalloc().

Also, I fixed the issue with LSM data not measured when using the IMA 
policy you had. Good catch.

Will post the updated patches today.

thanks,
  -lakshmi