On Fri, 2026-06-05 at 15:43 +0100, Yeoreum Yun wrote:
> To generate the boot_aggregate log in the IMA subsystem with
> TPM PCR values, the TPM driver must be built as built-in and
> must be probed before the IMA subsystem is initialized.
>
> However, when the TPM device operates over the FF-A protocol using
> the CRB interface, probing fails and returns -EPROBE_DEFER if
> the tpm_crb_ffa device — an FF-A device that provides the communication
> interface to the tpm_crb driver — has not yet been probed.
>
> To ensure the TPM device operating over the FF-A protocol with
> the CRB interface is probed before IMA initialization,
> the following conditions must be met:
>
> 1. The corresponding ffa_device must be registered,
> which is done via ffa_init().
>
> 2. The tpm_crb_driver must successfully probe this device via
> tpm_crb_ffa_init().
>
> 3. The tpm_crb driver using CRB over FF-A can then
> be probed successfully. (See crb_acpi_add() and
> tpm_crb_ffa_init() for reference.)
>
> Unfortunately, ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init()
> are all registered with device_initcall, which means
> crb_acpi_driver_init() may be invoked before ffa_init() and
> tpm_crb_ffa_init() are completed.
>
> When this occurs, probing the TPM device is deferred.
> However, the deferred probe can happen after the IMA subsystem
> has already been initialized, since IMA initialization is performed
> during late_initcall, and deferred_probe_initcall() is performed
> at the same level.
>
> And the similar situation is reported on TPM devices attached on SPI
> bus[0].
>
> To resolve this, introduce IMA_INIT_LATE_SYNC option to initialise
> IMA at late_inicall_sync so that IMA is initialized with the TPM
> device probed deferred.
>
> When this option is enabled, modules that access files in the
> initramfs through usermode helper calls such as request_module()
> during initcall must not be built-in. Otherwise, IMA may miss
> measuring those files [1].
>
> Link: https://lore.kernel.org/all/[email protected]/ [0]
> Link:
> https://lore.kernel.org/all/[email protected]/
> [1]
> Suggested-by: Mimi Zohar <[email protected]>
> Reviewed-by: Mimi Zohar <[email protected]>
> Signed-off-by: Yeoreum Yun <[email protected]>
> ---
> security/integrity/ima/Kconfig | 10 ++++++++++
> security/integrity/ima/ima_main.c | 4 ++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 862fbee2b174..75f71401fba3 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -332,4 +332,14 @@ config IMA_KEXEC_EXTRA_MEMORY_KB
> If set to the default value of 0, an extra half page of memory for
> those
> additional measurements will be allocated.
>
> +config IMA_INIT_LATE_SYNC
> + bool "Initialise IMA at late_initcall_sync"
> + default n
> + help
> + This option initialises IMA at late_initcall_sync for platforms
> + where TPM device probing is deferred.
> + When this option is enabled, modules that access files in the
> + initramfs through usermode helper calls such as request_module()
> + during initcall must not be built-in. Otherwise, IMA may miss
> + file measurements for them.
> endif
I fixed the merge conflict with the "ima: Exporting and deleting IMA measurement
records from kernel memory" patch set. These patches are now queued in next-
integrity-testing awaiting Paul's Ack.
Mimi
> diff --git a/security/integrity/ima/ima_main.c
> b/security/integrity/ima/ima_main.c
> index 5cea53fc36df..1cfae4b83dc5 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -1337,5 +1337,9 @@ DEFINE_LSM(ima) = {
> .order = LSM_ORDER_LAST,
> .blobs = &ima_blob_sizes,
> /* Start IMA after the TPM is available */
> +#ifndef CONFIG_IMA_INIT_LATE_SYNC
> .initcall_late = init_ima,
> +#else
> + .initcall_late_sync = init_ima,
> +#endif
> };
