[PATCH v3] ima: Access decompressed kernel module to verify appended signature

[Coiby Xu]

On Wed, Nov 19, 2025 at 08:29:22AM -0500, Mimi Zohar wrote:
>Hi Coiby,

Hi Mimi,

>
>On Wed, 2025-11-19 at 11:47 +0800, Coiby Xu wrote:
>> Currently, when in-kernel module decompression (CONFIG_MODULE_DECOMPRESS)
>> is enabled, IMA has no way to verify the appended module signature as it
>> can't decompress the module.
>>
>> Define a new kernel_read_file_id enumerate READING_MODULE_COMPRESSED so
>> IMA can know only to collect original module data hash on
>> READING_MODULE_COMPRESSED and defer appraising/measuring it until on
>> READING_MODULE when the module has been decompressed.
>
>This paragraph is a bit awkward.  Perhaps something like:
>
>-> so IMA can calculate the compressed kernel module data hash and defer
>measuring/appraising ...
>
>>
>> Before enabling in-kernel module decompression, a kernel module in
>> initramfs can still be loaded with ima_policy=secure_boot. So adjust the
>> kernel module rule in secure_boot policy to allow either an IMA
>> signature OR an appended signature i.e. to use
>> "appraise func=MODULE_CHECK appraise_type=imasig|modsig".
>>
>> Reported-by: Karel Srot <ksrot at redhat.com>
>> Suggested-by: Mimi Zohar <zohar at linux.ibm.com>
>> Suggested-by: Paul Moore <paul at paul-moore.com>
>> Signed-off-by: Coiby Xu <coxu at redhat.com>
>
>Thanks, Coiby!
>
>The patch applies cleanly to linus' tree, but needs to be applied to next-
>integrity.  Please re-base.

I've sent v4 which has been rebased onto next tree with improved
wording as suggested.

>
>-- 
>
>thanks,
>
>Mimi
>

-- 
Best regards,
Coiby