[WIP RFC PATCH 0/6] Generic Firmware Variable Filesystem

[Nayna]

On 06/03/2019 03:29 AM, Greg KH wrote:
> On Mon, Jun 03, 2019 at 04:04:32PM +1000, Daniel Axtens wrote:
>> Hi Nayna,
>>
>>>> As PowerNV moves towards secure boot, we need a place to put secure
>>>> variables. One option that has been canvassed is to make our secure
>>>> variables look like EFI variables. This is an early sketch of another
>>>> approach where we create a generic firmware variable file system,
>>>> fwvarfs, and an OPAL Secure Variable backend for it.
>>> Is there a need of new filesystem ? I am wondering why can't these be
>>> exposed via sysfs / securityfs ?
>>> Probably, something like... /sys/firmware/secureboot or
>>> /sys/kernel/security/secureboot/  ?
>> I suppose we could put secure variables in sysfs, but I'm not sure
>> that's what sysfs was intended for. I understand sysfs as "a
>> filesystem-based view of kernel objects" (from
>> Documentation/filesystems/configfs/configfs.txt), and I don't think a
>> secure variable is really a kernel object in the same way most other
>> things in sysfs are... but I'm open to being convinced.
> What makes them more "secure" than anything else that is in sysfs today?
> I didn't see anything in this patchset that provided "additional
> security", did I miss it?
>
>> securityfs seems to be reserved for LSMs, I don't think we can put
>> things there.
> Yeah, I wouldn't mess with that.

Thanks Greg for clarifying!! I am curious, the TPM exposes the BIOS event log to userspace via securityfs. Is there a reason for not exposing these security variables to userspace via securityfs as well?

Thanks & Regards,
    - Nayna