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

Nayna
2022-11-23T18:58:53Z

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