[RFC PATCH] ima: add a knob to make IMA be able to be disabled

[Baoquan He]

On 04/09/25 at 11:40am, Mimi Zohar wrote:
> On Wed, 2025-04-09 at 10:42 +0800, Baoquan He wrote:
......snip.. 
> > Thanks for confirming. I will consider how to fix it accordingly. Maybe
> > after Steven's patches are merged. That would be great if the buffer
> > allocating and storing can be skiped for kdump in Steven's patch. While
> > I am worried that could disrupt the progress of Steven's patches.
> 
> Agreed, let's get Steven's patch set upstreamed and then make the kdump
> exceptions.
> 
> - "ima: kexec: move IMA log copy from kexec load to execute" looks like it isn't
> copying the IMA measurement list records (kexec_post_load), but the memory for
> the IMA measurement list is being allocated (ima_alloc_kexec_file_buf).
> 
> - Do you really want to totally disable IMA for kdump or would disabling IMA-
> measurement be sufficient?  Remember there's already an option to disable IMA-
> appraisal.  Disabling just IMA-measurement would allow IMA-appraisal to continue
> to work.  Meaning based on policy the integrity of files - executables, kernel
> image, etc - could still be verified.
> 
> Without IMA-measurement:
> - No adding records to the IMA measurement list
> - No IMA measurement list pseudo securityfs files
> - No extending the TPM
> 
> With IMA-appraisal:
> - Integrity verification of files based on keys, keyrings
> - Loading keys

Currently, Kdump has no demand to do integrity verification based on
keys, keyrings, except of Coiby's LUKS support in kdump:

[PATCH v8 0/7] Support kdump with LUKS encryption by reusing LUKS volume keys
https://lore.kernel.org/all/20250207080818.129165-1-coxu@redhat.com/T/#u

I have talked to Coiby, he will do some investigations to see if loading
keys related to IMA or IMA-appraisal functionality is related to LUKS
support in kdump because the LUKS support in kdump also needs
store/restore keys/keyrings between normal kernel and kdump kernel.

> 
> Obviously my preference would be to add support to disable IMA-measurement in a
> kdump environment.
> 
> thanks,
> 
> Mimi
>