Re: Module compression & loadpin

[Jessica Yu <jeyu@kernel.org>]

+++ Lucas De Marchi [06/08/19 15:53 -0700]:
>+Jessica
>
>On Sat, Aug 3, 2019 at 9:50 AM Jack Rosenthal <jrosenth@chromium.org> wrote:
>>
>> Has anyone looked into what it may take to support both module
>> compression and loadpin (ensures modules come from trusted filesystem)?
>>
>> From my understanding, this is not supported as kmod currently does the
>> decompression of modules, and loadpin prefers fload_module as it can
>> tell where the module came from. (https://crbug.com/777204)
>>
>> In a gist, I am thinking supporting this scenario would require the
>> module decompression to happen on the kernel side. Wondering if anyone
>> has looked into this before I go making a solution...
>
>That's my thought as well. In order to use finit_module() with
>compressed modules we need to teach the kernel how to open it. It
>should not be difficult since kernel already has the decompression
>libraries. This also gives us access to another
>compression/decompression algorithms - but would be nice to have a
>correspondent implementation for modinfo.
>
>I planned to do that some years ago, but never implemented it. Nobody
>that I know of is currently working on that. It would be a very
>welcome contribution.

Indeed, I don't know of anyone currently working on that. I do not
think it should be that difficult, since as Lucas already mentioned we
already have multiple decompression libraries in the kernel to extract
the compressed kernel image on boot (see: lib/decompress.c and
friends), so at first glance, I don't think it would be too hard to
extend this functionality to the module loader. I'd welcome a patchset :)

Thanks,

Jessica