[PATCH v5 0/4] introduce IMA_INIT_LATE_SYNC option

[PATCH v5 0/4] introduce IMA_INIT_LATE_SYNC option

[Yeoreum Yun]

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 defered.

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 since they're the file accesses before the
initialisation of IMA [1].

Link: https://lore.kernel.org/all/aYXEepLhUouN5f99@earth.li/ [0]
Link: https://lore.kernel.org/all/2b3782398cc17ce9d355490a0c42ebce9120a9ae.camel@linux.ibm.com/ [1]

Patch history
=============
from v4 to v5:
  - rebase on v7.1-rc6
  - apply boot_aggreate name patch from @Jonathan and align it with
    IMA_INIT_LATE_SYNC option.
  - https://lore.kernel.org/all/20260525075404.3480282-1-yeoreum.yun@arm.com/

from v3 to v4:
  - rebase on v7.1-rc5
  - introduce IMA_INIT_LATE_SYNC option to control IMA initailisation.
  - https://lore.kernel.org/all/cover.1777036497.git.noodles@meta.com/

from v2 to v3:
  - Drop ff-a/pKVM diff (this seems to have a separate set of
    discussion)
  - Rework IMA delayed initialisation to avoid delaying when unnecessary
  - Ensure IMA log clearly indicates when we've initialised late
  - https://lore.kernel.org/all/20260422162449.1814615-1-yeoreum.yun@arm.com/

from v1 to v2:
  - add notifier to make ffa-driver pkvm initialised.
  - modify to try initailisation again when IMA coudln't find proper TPM device.
  - https://lore.kernel.org/all/20260417175759.3191279-1-yeoreum.yun@arm.com/#t


Jonathan McDowell (1):
  security: ima: rename boot_aggregate when ima is initialised at
    late_sync

Yeoreum Yun (3):
  security: lsm: allow LSMs to register for late_initcall_sync init
  security: ima: introduce IMA_INIT_LATE_SYNC option
  tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in

 drivers/char/tpm/tpm_crb_ffa.c            | 18 +++---------------
 include/linux/lsm_hooks.h                 |  2 ++
 security/integrity/ima/Kconfig            | 10 ++++++++++
 security/integrity/ima/ima.h              |  1 +
 security/integrity/ima/ima_init.c         | 15 +++++++++++----
 security/integrity/ima/ima_main.c         |  4 ++++
 security/integrity/ima/ima_template_lib.c |  3 ++-
 security/lsm_init.c                       | 13 +++++++++++--
 8 files changed, 44 insertions(+), 22 deletions(-)


base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

[PATCH v5 1/4] security: lsm: allow LSMs to register for late_initcall_sync init

[Yeoreum Yun]

There are situations where LSMs have dependencies that might mean they
want to be initialised later in the boot process, to ensure those
dependencies are available. In particular there are some TPM setups (Arm
FF-A devices, SPI attached TPMs) required by IMA which are not
guaranteed to be initialised for regular initcall_late.

Add an initcall_late_sync option that can be used in these situations.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 include/linux/lsm_hooks.h |  2 ++
 security/lsm_init.c       | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index b4f8cad53ddb..c4488c4a6d8a 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -167,6 +167,7 @@ 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;
@@ -182,6 +183,7 @@ 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/lsm_init.c b/security/lsm_init.c
index 7c0fd17f1601..a1ad641811de 100644
--- a/security/lsm_init.c
+++ b/security/lsm_init.c
@@ -556,13 +556,22 @@ 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}

[PATCH v5 2/4] security: ima: introduce IMA_INIT_LATE_SYNC option

[Yeoreum Yun]

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/aYXEepLhUouN5f99@earth.li/ [0]
Link: https://lore.kernel.org/all/2b3782398cc17ce9d355490a0c42ebce9120a9ae.camel@linux.ibm.com/ [1]
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 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
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
 };
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

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

[Yeoreum Yun]

From: Jonathan McDowell <noodles@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@meta.com>
[yeoreum.yun@arm.com: modified to align with the IMA_INIT_LATE_SYNC change]
---
 security/integrity/ima/ima.h              |  1 +
 security/integrity/ima/ima_init.c         | 15 +++++++++++----
 security/integrity/ima/ima_template_lib.c |  3 ++-
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 69e9bf0b82c6..194b195cec1e 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -66,6 +66,7 @@ extern struct ima_algo_desc *ima_algo_array __ro_after_init;
 extern int ima_appraise;
 extern struct tpm_chip *ima_tpm_chip;
 extern const char boot_aggregate_name[];
+extern const char boot_aggregate_late_name[];
 
 /* IMA event related data */
 struct ima_event_data {
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index a2f34f2d8ad7..4c24bd535466 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -22,6 +22,7 @@
 
 /* name for boot aggregate entry */
 const char boot_aggregate_name[] = "boot_aggregate";
+const char boot_aggregate_late_name[] = "boot_aggregate_late";
 struct tpm_chip *ima_tpm_chip;
 
 /* Add the boot aggregate to the IMA measurement list and extend
@@ -45,11 +46,11 @@ static int __init ima_add_boot_aggregate(void)
 	const char *audit_cause = "ENOMEM";
 	struct ima_template_entry *entry;
 	struct ima_iint_cache tmp_iint, *iint = &tmp_iint;
-	struct ima_event_data event_data = { .iint = iint,
-					     .filename = boot_aggregate_name };
+	struct ima_event_data event_data = { .iint = iint };
 	struct ima_max_digest_data hash;
 	struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
 						struct ima_digest_data, hdr);
+	const char *filename;
 	int result = -ENOMEM;
 	int violation = 0;
 
@@ -59,6 +60,12 @@ static int __init ima_add_boot_aggregate(void)
 	iint->ima_hash->algo = ima_hash_algo;
 	iint->ima_hash->length = hash_digest_size[ima_hash_algo];
 
+	if (IS_ENABLED(CONFIG_IMA_INIT_LATE_SYNC))
+		filename = boot_aggregate_late_name;
+	else
+		filename = boot_aggregate_name;
+	event_data.filename = filename;
+
 	/*
 	 * With TPM 2.0 hash agility, TPM chips could support multiple TPM
 	 * PCR banks, allowing firmware to configure and enable different
@@ -86,7 +93,7 @@ static int __init ima_add_boot_aggregate(void)
 	}
 
 	result = ima_store_template(entry, violation, NULL,
-				    boot_aggregate_name,
+				    filename,
 				    CONFIG_IMA_MEASURE_PCR_IDX);
 	if (result < 0) {
 		ima_free_template_entry(entry);
@@ -95,7 +102,7 @@ static int __init ima_add_boot_aggregate(void)
 	}
 	return 0;
 err_out:
-	integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL, boot_aggregate_name, op,
+	integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL, filename, op,
 			    audit_cause, result, 0);
 	return result;
 }
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 0e627eac9c33..8a89236f926c 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -363,7 +363,8 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
 		goto out;
 	}
 
-	if ((const char *)event_data->filename == boot_aggregate_name) {
+	if ((const char *)event_data->filename == boot_aggregate_name ||
+	    (const char *)event_data->filename == boot_aggregate_late_name) {
 		if (ima_tpm_chip) {
 			hash.hdr.algo = HASH_ALGO_SHA1;
 			result = ima_calc_boot_aggregate(hash_hdr);
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

[PATCH v5 4/4] tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in

[Yeoreum Yun]

commit 746d9e9f62a6 ("tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's build_in")
probe tpm_crb_ffa forcefully when it's built-in to integrate with IMA.

However, IMA now provides the IMA_INIT_LATE_SYNC build option, which
initialises IMA at the late_initcall_sync level, so this change is no
longer required.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 drivers/char/tpm/tpm_crb_ffa.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 99f1c1e5644b..025c4d4b17ca 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -177,23 +177,13 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
  */
 int tpm_crb_ffa_init(void)
 {
-	int ret = 0;
-
-	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
-		ret = ffa_register(&tpm_crb_ffa_driver);
-		if (ret) {
-			tpm_crb_ffa = ERR_PTR(-ENODEV);
-			return ret;
-		}
-	}
-
 	if (!tpm_crb_ffa)
-		ret = -ENOENT;
+		return -ENOENT;
 
 	if (IS_ERR_VALUE(tpm_crb_ffa))
-		ret = -ENODEV;
+		return -ENODEV;
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
 
@@ -405,9 +395,7 @@ static struct ffa_driver tpm_crb_ffa_driver = {
 	.id_table = tpm_crb_ffa_device_id,
 };
 
-#ifdef MODULE
 module_ffa_driver(tpm_crb_ffa_driver);
-#endif
 
 MODULE_AUTHOR("Arm");
 MODULE_DESCRIPTION("TPM CRB FFA driver");
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

Re: [PATCH v5 4/4] tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in

[Jarkko Sakkinen]

On Mon, Jun 01, 2026 at 03:27:49PM +0100, Yeoreum Yun wrote:
> commit 746d9e9f62a6 ("tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's build_in")
> probe tpm_crb_ffa forcefully when it's built-in to integrate with IMA.
> 
> However, IMA now provides the IMA_INIT_LATE_SYNC build option, which
> initialises IMA at the late_initcall_sync level, so this change is no
> longer required.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

> ---
>  drivers/char/tpm/tpm_crb_ffa.c | 18 +++---------------
>  1 file changed, 3 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
> index 99f1c1e5644b..025c4d4b17ca 100644
> --- a/drivers/char/tpm/tpm_crb_ffa.c
> +++ b/drivers/char/tpm/tpm_crb_ffa.c
> @@ -177,23 +177,13 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
>   */
>  int tpm_crb_ffa_init(void)
>  {
> -	int ret = 0;
> -
> -	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
> -		ret = ffa_register(&tpm_crb_ffa_driver);
> -		if (ret) {
> -			tpm_crb_ffa = ERR_PTR(-ENODEV);
> -			return ret;
> -		}
> -	}
> -
>  	if (!tpm_crb_ffa)
> -		ret = -ENOENT;
> +		return -ENOENT;
>  
>  	if (IS_ERR_VALUE(tpm_crb_ffa))
> -		ret = -ENODEV;
> +		return -ENODEV;
>  
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
>  
> @@ -405,9 +395,7 @@ static struct ffa_driver tpm_crb_ffa_driver = {
>  	.id_table = tpm_crb_ffa_device_id,
>  };
>  
> -#ifdef MODULE
>  module_ffa_driver(tpm_crb_ffa_driver);
> -#endif
>  
>  MODULE_AUTHOR("Arm");
>  MODULE_DESCRIPTION("TPM CRB FFA driver");
> -- 
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
> 

BR, Jarkko