linux-kernel - Re: [PATCH 2/4] fs: define a firmware security filesystem named fwsecurityfs

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Date:   Wed, 23 Nov 2022 13:57:58 -0500
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Nayna Jain <nayna@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-security-module <linux-security-module@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com,
        christophe.leroy@...roup.eu, Dov Murik <dovmurik@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Russell Currey <ruscur@...sell.cc>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Stefan Berger <stefanb@...ux.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: Re: [PATCH 2/4] fs: define a firmware security filesystem named
 fwsecurityfs


On 11/23/22 10:57, Greg Kroah-Hartman wrote:
> On Wed, Nov 23, 2022 at 10:05:49AM -0500, Nayna wrote:
>> On 11/22/22 18:21, Nayna wrote:
>>>  From the perspective of our use case, we need to expose firmware
>>> security objects to userspace for management. Not all of the objects
>>> pre-exist and we would like to allow root to create them from userspace.
>>>
>>>  From a unification perspective, I have considered a common location at
>>> /sys/firmware/security for managing any platform's security objects. And
>>> I've proposed a generic filesystem, which could be used by any platform
>>> to represent firmware security objects via /sys/firmware/security.
>>>
>>> Here are some alternatives to generic filesystem in discussion:
>>>
>>> 1. Start with a platform-specific filesystem. If more platforms would
>>> like to use the approach, it can be made generic. We would still have a
>>> common location of /sys/firmware/security and new code would live in
>>> arch. This is my preference and would be the best fit for our use case.
>>>
>>> 2. Use securityfs.  This would mean modifying it to satisfy other use
>>> cases, including supporting userspace file creation. I don't know if the
>>> securityfs maintainer would find that acceptable. I would also still
>>> want some way to expose variables at /sys/firmware/security.
>>>
>>> 3. Use a sysfs-based approach. This would be a platform-specific
>>> implementation. However, sysfs has a similar issue to securityfs for
>>> file creation. When I tried it in RFC v1[1], I had to implement a
>>> workaround to achieve that.
>>>
>>> [1] https://lore.kernel.org/linuxppc-dev/20220122005637.28199-3-nayna@linux.ibm.com/
>>>
>> Hi Greg,
>>
>> Based on the discussions so far, is Option 1, described above, an acceptable
>> next step?
> No, as I said almost a year ago, I do not want to see platform-only
> filesystems going and implementing stuff that should be shared by all
> platforms.

Given there are no other exploiters for fwsecurityfs and there should be 
no platform-specific fs, would modifying sysfs now to let userspace 
create files cleanly be the way forward? Or, if we should strongly 
consider securityfs, which would result in updating securityfs to allow 
userspace creation of files and then expose variables via a more 
platform-specific directory /sys/kernel/security/pks? We want to pick 
the best available option and would find some hints on direction helpful 
before we develop the next patch.

Thanks & Regards,

       - Nayna