[PATCH v5 3/4] security: ima: rename boot_aggregate when ima is initialised at late_sync

[Mimi Zohar]

On Mon, 2026-06-01 at 15:27 +0100, Yeoreum Yun wrote:
> From: Jonathan McDowell <noodles at meta.com>
> 
> The Linux IMA (Integrity Measurement Architecture) subsystem used for
> secure boot, file integrity, or remote attestation cannot be a loadable
> module for few reasons listed below:
> 
>  o Boot-Time Integrity: IMA’s main role is to measure and appraise files
>    before they are used. This includes measuring critical system files
>    during early boot (e.g., init, init scripts, login binaries). If IMA
>    were a module, it would be loaded too late to cover those.
> 
>  o TPM Dependency: IMA integrates tightly with the TPM to record
>    measurements into PCRs. The TPM must be initialized early (ideally
>    before init_ima()), which aligns with IMA being built-in.
> 
>  o Security Model: IMA is part of a Trusted Computing Base (TCB). Making
>    it a module would weaken the security model, as a potentially
>    compromised system could delay or tamper with its initialization.
> 
> IMA must be built-in to ensure it starts measuring from the earliest
> possible point in boot which inturn implies TPM must be initialised and
> ready to use before IMA.
> 
> Unfortunately some TPM drivers (such as Arm FF-A, or SPI attached TPM
> devices) are not reliably available during the initcall_late stage,
> resulting in a log error:
> 
>   ima: No TPM chip found, activating TPM-bypass!
> 
> To address this issue, IMA_INIT_LATE_SYNC is introduced.
> However, a remote attestation service cannot determine when IMA has been
> initialized because the boot_aggregate measurement name remains unchanged,
> even though IMA is initialized later at late_initcall_sync when
> IMA_INIT_LATE_SYNC is enabled.
> 
> Therefore, use a distinct boot_aggregate name when IMA_INIT_LATE_SYNC
> is enabled, allowing the remote attestation service to identify
> when IMA has been initialized.
> 
> Signed-off-by: Jonathan McDowell <noodles at meta.com>
> [yeoreum.yun at arm.com: modified to align with the IMA_INIT_LATE_SYNC change]

Thanks, Yeoreum. This version requires your Signed-off-by tag as well as
Jonathan's.  Otherwise the patch looks good.

Mimi