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

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Message-ID: <yiwtnidayji53irhrowznu75ajedrsu6pwh7xzjplcyzmifz6u@7epealeg3ssa>
Date: Wed, 19 Nov 2025 22:05:50 +0800
From: Coiby Xu <coxu@...hat.com>
To: Mimi Zohar <zohar@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, Karel Srot <ksrot@...hat.com>, 
	Paul Moore <paul@...l-moore.com>, Luis Chamberlain <mcgrof@...nel.org>, 
	Petr Pavlu <petr.pavlu@...e.com>, Daniel Gomez <da.gomez@...nel.org>, 
	Sami Tolvanen <samitolvanen@...gle.com>, Roberto Sassu <roberto.sassu@...wei.com>, 
	Dmitry Kasatkin <dmitry.kasatkin@...il.com>, Eric Snowberg <eric.snowberg@...cle.com>, 
	James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Fan Wu <wufan@...nel.org>, 
	Stephen Smalley <stephen.smalley.work@...il.com>, Ondrej Mosnacek <omosnace@...hat.com>, 
	open list <linux-kernel@...r.kernel.org>, "open list:MODULE SUPPORT" <linux-modules@...r.kernel.org>, 
	"open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>, "open list:SELINUX SECURITY MODULE" <selinux@...r.kernel.org>
Subject: Re: [PATCH v3] ima: Access decompressed kernel module to verify
 appended signature

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@...hat.com>
>> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
>> Suggested-by: Paul Moore <paul@...l-moore.com>
>> Signed-off-by: Coiby Xu <coxu@...hat.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