[RFC PATCH v2 1/4] security: ima: call ima_init() again at late_initcall_sync for defered TPM

[Yeoreum Yun <yeoreum.yun@arm.com>]

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, call ima_init() again at 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@arm.com>
---
 include/linux/lsm_hooks.h           |  2 +
 security/integrity/ima/ima.h        |  4 +-
 security/integrity/ima/ima_init.c   | 10 +++-
 security/integrity/ima/ima_main.c   | 76 +++++++++++++++++++++++------
 security/integrity/ima/ima_policy.c |  3 ++
 security/lsm_init.c                 | 13 ++++-
 6 files changed, 87 insertions(+), 21 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.h b/security/integrity/ima/ima.h
index 89ebe98ffc5e..75ee7ad184d0 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -62,6 +62,8 @@ extern int ima_hash_algo_idx __ro_after_init;
 extern int ima_extra_slots __ro_after_init;
 extern struct ima_algo_desc *ima_algo_array __ro_after_init;

+extern bool ima_initialised __ro_after_init;
+
 extern int ima_appraise;
 extern struct tpm_chip *ima_tpm_chip;
 extern const char boot_aggregate_name[];
@@ -257,7 +259,7 @@ static inline void ima_measure_kexec_event(const char *event_name) {}
 extern bool ima_canonical_fmt;

 /* Internal IMA function definitions */
-int ima_init(void);
+int ima_init(bool late);
 int ima_fs_init(void);
 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 			   const char *op, struct inode *inode,
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index a2f34f2d8ad7..c28c71090ad2 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -115,13 +115,19 @@ void __init ima_load_x509(void)
 }
 #endif

-int __init ima_init(void)
+int __init ima_init(bool late)
 {
 	int rc;

 	ima_tpm_chip = tpm_default_chip();
-	if (!ima_tpm_chip)
+	if (!ima_tpm_chip) {
+		if (!late) {
+			pr_info("Defer initialisation to the late_initcall_sync stage.\n");
+			return -EPROBE_DEFER;
+		}
+
 		pr_info("No TPM chip found, activating TPM-bypass!\n");
+	}

 	rc = integrity_init_keyring(INTEGRITY_KEYRING_IMA);
 	if (rc)
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 1d6229b156fb..ac444ee600e2 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -38,6 +38,7 @@ int ima_appraise;
 #endif

 int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
+bool ima_initialised __ro_after_init = false;
 static int hash_setup_done;
 static int ima_disabled __ro_after_init;

@@ -1237,6 +1238,35 @@ static int ima_kernel_module_request(char *kmod_name)

 #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */

+static int __init init_ima_core(bool late)
+{
+	int err;
+
+	if (ima_initialised)
+		return 0;
+
+	err = ima_init(late);
+	if (err == -EPROBE_DEFER)
+		return 0;
+
+	if (err && strcmp(hash_algo_name[ima_hash_algo],
+			  CONFIG_IMA_DEFAULT_HASH) != 0) {
+		pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
+			hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
+		hash_setup_done = 0;
+		hash_setup(CONFIG_IMA_DEFAULT_HASH);
+		err = ima_init(late);
+	}
+
+	if (!err) {
+		ima_update_policy_flags();
+		ima_initialised = true;
+	} else
+		ima_disabled = 1;
+
+	return err;
+}
+
 static int __init init_ima(void)
 {
 	int error;
@@ -1250,30 +1280,42 @@ static int __init init_ima(void)
 	ima_appraise_parse_cmdline();
 	ima_init_template_list();
 	hash_setup(CONFIG_IMA_DEFAULT_HASH);
-	error = ima_init();
-
-	if (error && strcmp(hash_algo_name[ima_hash_algo],
-			    CONFIG_IMA_DEFAULT_HASH) != 0) {
-		pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
-			hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
-		hash_setup_done = 0;
-		hash_setup(CONFIG_IMA_DEFAULT_HASH);
-		error = ima_init();
-	}
-
-	if (error)
-		return error;

 	error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
-	if (error)
+	if (error) {
 		pr_warn("Couldn't register LSM notifier, error %d\n", error);
+		goto disable_ima;
+	}

-	if (!error)
-		ima_update_policy_flags();
+	error = init_ima_core(false);
+	if (error) {
+		unregister_blocking_lsm_notifier(&ima_lsm_policy_notifier);
+		goto disable_ima;
+	}
+
+	return 0;

+disable_ima:
+	ima_disabled = 1;
 	return error;
 }

+static int __init late_init_ima(void)
+{
+	int err;
+
+	if (ima_disabled)
+		return 0;
+
+	err = init_ima_core(true);
+	if (err) {
+		unregister_blocking_lsm_notifier(&ima_lsm_policy_notifier);
+		ima_disabled = 1;
+	}
+
+	return err;
+}
+
 static struct security_hook_list ima_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
 	LSM_HOOK_INIT(bprm_creds_for_exec, ima_bprm_creds_for_exec),
@@ -1321,4 +1363,6 @@ DEFINE_LSM(ima) = {
 	.blobs = &ima_blob_sizes,
 	/* Start IMA after the TPM is available */
 	.initcall_late = init_ima,
+	/* Start IMA late in case of probing TPM is deferred. */
+	.initcall_late_sync = late_init_ima,
 };
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index bf2d7ba4c14a..c3bcc3521c81 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -501,6 +501,9 @@ static void ima_lsm_update_rules(void)
 int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 			  void *lsm_data)
 {
+	if (!ima_initialised)
+		return NOTIFY_DONE;
+
 	if (event != LSM_POLICY_CHANGE)
 		return NOTIFY_DONE;

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}