Re: [RFC PATCH 1/4] security: ima: move ima_init into late_initcall_sync

[Mimi Zohar]

On Fri, 2026-04-17 at 18:57 +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.
> 
> To resolve this, move ima_init() into late_inicall_sync level
> so that let IMA not miss TPM PCR value when generating boot_aggregate
> log though TPM device presents in the system.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>

IMA should be initialized as early as possible. I'm really hesitant to defer
ima_init() to late_initcall_sync() for systems that the TPM is currently
initialized in time. For these systems, continue initializing IMA at
late_initcall(). As a compromise for those systems that the TPM isn't properly
initialized in time, define and instantiate the late_initcall_sync().

ima_init() would need to differentiate between the late_initcall and
late_initcall_sync.  On late_initcall(), instead of saying "No TPM chip found,
activating TPM-bypass!",  it should say "No TPM chip found, deferring to
late_initcall_sync" or something similar.

thanks,

Mimi

> ---
>  include/linux/lsm_hooks.h         |  2 ++
>  security/integrity/ima/ima_main.c |  2 +-
>  security/lsm_init.c               | 13 +++++++++++--
>  3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index d48bf0ad26f4..88fe105b7f00 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -166,6 +166,7 @@ enum lsm_order {
>   * @initcall_fs: LSM callback for fs_initcall setup, optional
>   * @initcall_device: LSM callback for device_initcall() setup, optional
>   * @initcall_late: LSM callback for late_initcall() setup, optional
> + * @initcall_late_sync: LSM callback for late_initcall_sync() setup, optional
>   */
>  struct lsm_info {
>  	const struct lsm_id *id;
> @@ -181,6 +182,7 @@ struct lsm_info {
>  	int (*initcall_fs)(void);
>  	int (*initcall_device)(void);
>  	int (*initcall_late)(void);
> +	int (*initcall_late_sync)(void);
>  };
> 
>  #define DEFINE_LSM(lsm)							\
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 1d6229b156fb..ace280fa3212 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -1320,5 +1320,5 @@ DEFINE_LSM(ima) = {
>  	.order = LSM_ORDER_LAST,
>  	.blobs = &ima_blob_sizes,
>  	/* Start IMA after the TPM is available */
> -	.initcall_late = init_ima,
> +	.initcall_late_sync = init_ima,
>  };
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index 573e2a7250c4..4e5c59beb82a 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -547,13 +547,22 @@ device_initcall(security_initcall_device);
>   * security_initcall_late - Run the LSM late initcalls
>   */
>  static int __init security_initcall_late(void)
> +{
> +	return lsm_initcall(late);
> +}
> +late_initcall(security_initcall_late);
> +
> +/**
> + * security_initcall_late_sync - Run the LSM late initcalls sync
> + */
> +static int __init security_initcall_late_sync(void)
>  {
>  	int rc;
> 
> -	rc = lsm_initcall(late);
> +	rc = lsm_initcall(late_sync);
>  	lsm_pr_dbg("all enabled LSMs fully activated\n");
>  	call_blocking_lsm_notifier(LSM_STARTED_ALL, NULL);
> 
>  	return rc;
>  }
> -late_initcall(security_initcall_late);
> +late_initcall_sync(security_initcall_late_sync);
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>