[PATCH v9 0/3] IMA: Deferred measurement of keys

[PATCH v9 0/3] IMA: Deferred measurement of keys

[Lakshmi Ramasubramanian]

The IMA subsystem supports measuring asymmetric keys when the key is
created or updated[1]. But keys created or updated before a custom IMA
policy is loaded are currently not measured.  This includes keys added,
for instance, to either the .ima or .builtin_trusted_keys keyrings, which
happens early in the boot process.

Measuring the early boot keys, by design, requires loading a custom IMA
policy.  This change adds support for queuing keys created or updated
before a custom IMA policy is loaded.  The queued keys are processed when
a custom policy is loaded.  Keys created or updated after a custom policy
is loaded are measured immediately (not queued).  In the case when a
custom policy is not loaded within 5 minutes of IMA initialization, the
queued keys are freed.

[1] https://lore.kernel.org/linux-integrity/20191211164707.4698-1-nramas@linux.microsoft.com/

Changelog:

  v9

  => Rebased the changes to v5.5-rc7
  => Defined an intermediate Kconfig boolean option namely
     IMA_QUEUE_EARLY_BOOT_KEYS to declare the deferred key
     measurement functions.
  => Use delayed workqueue to free the queued keys when a custom IMA
     policy is not loaded.

  v8

  => Rebased the changes to linux-next
  => Need to apply the following patch first
  https://lore.kernel.org/linux-integrity/20200108160508.5938-1-nramas@linux.microsoft.com/

  v7

  => Updated cover letter per Mimi's suggestions.
  => Updated "Reported-by" tag to be specific about
     the issues fixed in the patch.

  v6

  => Replaced mutex with a spinlock to sychronize access to
     queued keys. This fixes the problem reported by
     "kernel test robot <rong.a.chen@intel.com>"
     https://lore.kernel.org/linux-integrity/2a831fe9-30e5-63b4-af10-a69f327f7fb7@linux.microsoft.com/T/#t
  => Changed ima_queue_key() to a static function. This fixes
     the issue reported by "kbuild test robot <lkp@intel.com>"
     https://lore.kernel.org/linux-integrity/1577370464.4487.10.camel@linux.ibm.com/
  => Added the patch to free the queued keys if a custom IMA policy
     was not loaded to this patch set.

  v5

  => Removed temp keys list in ima_process_queued_keys()

  v4

  => Check and set ima_process_keys flag with mutex held.

  v3

  => Defined ima_process_keys flag to be static.
  => Set ima_process_keys with ima_keys_mutex held.
  => Added a comment in ima_process_queued_keys() function
     to state the use of temporary list for keys.

  v2

  => Rebased the changes to v5.5-rc1
  => Updated function names, variable names, and code comments
     to be less verbose.

  v1

  => Code cleanup

  v0

  => Based changes on v5.4-rc8
  => The following patchsets should be applied in that order
     https://lore.kernel.org/linux-integrity/1572492694-6520-1-git-send-email-zohar@linux.ibm.com
     https://lore.kernel.org/linux-integrity/20191204224131.3384-1-nramas@linux.microsoft.com/
  => Added functions to queue and dequeue keys, and process
     the queued keys when custom IMA policies are applied.

Lakshmi Ramasubramanian (3):
  IMA: Define workqueue for early boot key measurements
  IMA: Call workqueue functions to measure queued keys
  IMA: Defined delayed workqueue to free the queued keys

 security/integrity/ima/Kconfig               |   5 +
 security/integrity/ima/Makefile              |   1 +
 security/integrity/ima/ima.h                 |  24 +++
 security/integrity/ima/ima_asymmetric_keys.c |   8 +
 security/integrity/ima/ima_init.c            |   8 +-
 security/integrity/ima/ima_policy.c          |   3 +
 security/integrity/ima/ima_queue_keys.c      | 171 +++++++++++++++++++
 7 files changed, 219 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/ima/ima_queue_keys.c

-- 
2.17.1

[PATCH v9 1/3] IMA: Define workqueue for early boot key measurements

[Lakshmi Ramasubramanian]

Measuring keys requires a custom IMA policy to be loaded.
Keys created or updated before a custom IMA policy is loaded should
be queued and the keys should be processed after a custom policy
is loaded.

This patch defines workqueue for queuing keys when a custom IMA policy
has not yet been loaded. An intermediate Kconfig boolean option namely
IMA_QUEUE_EARLY_BOOT_KEYS is used to declare the workqueue functions.

A flag namely ima_process_keys is used to check if the key should be
queued or should be processed immediately.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 security/integrity/ima/Kconfig          |   5 +
 security/integrity/ima/Makefile         |   1 +
 security/integrity/ima/ima.h            |  22 ++++
 security/integrity/ima/ima_queue_keys.c | 137 ++++++++++++++++++++++++
 4 files changed, 165 insertions(+)
 create mode 100644 security/integrity/ima/ima_queue_keys.c

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 6bec78eeeae8..711ff10fa36e 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -317,3 +317,8 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
 	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
 	default y
 
+config IMA_QUEUE_EARLY_BOOT_KEYS
+	bool
+	depends on IMA_MEASURE_ASYMMETRIC_KEYS
+	depends on SYSTEM_TRUSTED_KEYRING
+	default y
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 3e9d0ad68c7b..064a256f8725 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -13,3 +13,4 @@ ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
 obj-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
+obj-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index f06238e41a7c..905ed2f7f778 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -205,6 +205,28 @@ extern const char *const func_tokens[];
 
 struct modsig;
 
+#ifdef CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS
+/*
+ * To track keys that need to be measured.
+ */
+struct ima_key_entry {
+	struct list_head list;
+	void *payload;
+	size_t payload_len;
+	char *keyring_name;
+};
+bool ima_should_queue_key(void);
+bool ima_queue_key(struct key *keyring, const void *payload,
+		   size_t payload_len);
+void ima_process_queued_keys(void);
+#else
+static inline bool ima_should_queue_key(void) { return false; }
+static inline bool ima_queue_key(struct key *keyring,
+				 const void *payload,
+				 size_t payload_len) { return false; }
+static inline void ima_process_queued_keys(void) {}
+#endif /* CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS */
+
 /* LIM API function definitions */
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
 		   int mask, enum ima_hooks func, int *pcr,
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
new file mode 100644
index 000000000000..9b561f2b86db
--- /dev/null
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * File: ima_queue_keys.c
+ *       Enables deferred processing of keys
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <keys/asymmetric-type.h>
+#include "ima.h"
+
+/*
+ * Flag to indicate whether a key can be processed
+ * right away or should be queued for processing later.
+ */
+static bool ima_process_keys;
+
+/*
+ * To synchronize access to the list of keys that need to be measured
+ */
+static DEFINE_MUTEX(ima_keys_lock);
+static LIST_HEAD(ima_keys);
+
+static void ima_free_key_entry(struct ima_key_entry *entry)
+{
+	if (entry) {
+		kfree(entry->payload);
+		kfree(entry->keyring_name);
+		kfree(entry);
+	}
+}
+
+static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
+						 const void *payload,
+						 size_t payload_len)
+{
+	int rc = 0;
+	struct ima_key_entry *entry;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (entry) {
+		entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
+		entry->keyring_name = kstrdup(keyring->description,
+					      GFP_KERNEL);
+		entry->payload_len = payload_len;
+	}
+
+	if ((entry == NULL) || (entry->payload == NULL) ||
+	    (entry->keyring_name == NULL)) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&entry->list);
+
+out:
+	if (rc) {
+		ima_free_key_entry(entry);
+		entry = NULL;
+	}
+
+	return entry;
+}
+
+bool ima_queue_key(struct key *keyring, const void *payload,
+		   size_t payload_len)
+{
+	bool queued = false;
+	struct ima_key_entry *entry;
+
+	entry = ima_alloc_key_entry(keyring, payload, payload_len);
+	if (!entry)
+		return false;
+
+	mutex_lock(&ima_keys_lock);
+	if (!ima_process_keys) {
+		list_add_tail(&entry->list, &ima_keys);
+		queued = true;
+	}
+	mutex_unlock(&ima_keys_lock);
+
+	if (!queued)
+		ima_free_key_entry(entry);
+
+	return queued;
+}
+
+/*
+ * ima_process_queued_keys() - process keys queued for measurement
+ *
+ * This function sets ima_process_keys to true and processes queued keys.
+ * From here on keys will be processed right away (not queued).
+ */
+void ima_process_queued_keys(void)
+{
+	struct ima_key_entry *entry, *tmp;
+	bool process = false;
+
+	if (ima_process_keys)
+		return;
+
+	/*
+	 * Since ima_process_keys is set to true, any new key will be
+	 * processed immediately and not be queued to ima_keys list.
+	 * First one setting the ima_process_keys flag to true will
+	 * process the queued keys.
+	 */
+	mutex_lock(&ima_keys_lock);
+	if (!ima_process_keys) {
+		ima_process_keys = true;
+		process = true;
+	}
+	mutex_unlock(&ima_keys_lock);
+
+	if (!process)
+		return;
+
+
+	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
+		process_buffer_measurement(entry->payload,
+					   entry->payload_len,
+					   entry->keyring_name,
+					   KEY_CHECK, 0,
+					   entry->keyring_name);
+		list_del(&entry->list);
+		ima_free_key_entry(entry);
+	}
+}
+
+inline bool ima_should_queue_key(void)
+{
+	return !ima_process_keys;
+}
-- 
2.17.1

[PATCH v9 2/3] IMA: Call workqueue functions to measure queued keys

[Lakshmi Ramasubramanian]

Measuring keys requires a custom IMA policy to be loaded.
Keys should be queued for measurement if a custom IMA policy
is not yet loaded. Keys queued for measurement, if any, should be
processed when a custom IMA policy is loaded.

This patch updates the IMA hook function ima_post_key_create_or_update()
to queue the key if a custom IMA policy has not yet been loaded.
And, ima_update_policy() function, which is called when
a custom IMA policy is loaded, is updated to process queued keys.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 security/integrity/ima/ima_asymmetric_keys.c | 8 ++++++++
 security/integrity/ima/ima_policy.c          | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index fea2e7dd3b09..7678f0e3e84d 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -30,6 +30,8 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 				   const void *payload, size_t payload_len,
 				   unsigned long flags, bool create)
 {
+	bool queued = false;
+
 	/* Only asymmetric keys are handled by this hook. */
 	if (key->type != &key_type_asymmetric)
 		return;
@@ -37,6 +39,12 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 	if (!payload || (payload_len == 0))
 		return;
 
+	if (ima_should_queue_key())
+		queued = ima_queue_key(keyring, payload, payload_len);
+
+	if (queued)
+		return;
+
 	/*
 	 * keyring->description points to the name of the keyring
 	 * (such as ".builtin_trusted_keys", ".ima", etc.) to
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 3b16b190ae9b..f2fc24511cf4 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -807,6 +807,9 @@ void ima_update_policy(void)
 		kfree(arch_policy_entry);
 	}
 	ima_update_policy_flag();
+
+	/* Custom IMA policy has been loaded */
+	ima_process_queued_keys();
 }
 
 /* Keep the enumeration in sync with the policy_tokens! */
-- 
2.17.1

[PATCH v9 3/3] IMA: Defined delayed workqueue to free the queued keys

[Lakshmi Ramasubramanian]

Keys queued for measurement should be freed if a custom IMA policy
was not loaded. Otherwise, the keys will remain queued forever
consuming kernel memory.

This patch defines a delayed workqueue to handle the above scenario.
The workqueue handler is setup to execute 5 minutes after IMA
initialization is completed.

If a custom IMA policy is loaded before the workqueue handler is
scheduled to execute, the workqueue task is cancelled and any queued keys
are processed for measurement. But if a custom policy was not loaded then
the queued keys are just freed when the delayed workqueue handler is run.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reported-by: kernel test robot <rong.a.chen@intel.com> # sleeping
function called from invalid context
Reported-by: kbuild test robot <lkp@intel.com> # redefinition of
ima_init_key_queue() function.
---
 security/integrity/ima/ima.h            |  2 ++
 security/integrity/ima/ima_init.c       |  8 ++++-
 security/integrity/ima/ima_queue_keys.c | 44 ++++++++++++++++++++++---
 3 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 905ed2f7f778..64317d95363e 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -215,11 +215,13 @@ struct ima_key_entry {
 	size_t payload_len;
 	char *keyring_name;
 };
+void ima_init_key_queue(void);
 bool ima_should_queue_key(void);
 bool ima_queue_key(struct key *keyring, const void *payload,
 		   size_t payload_len);
 void ima_process_queued_keys(void);
 #else
+static inline void ima_init_key_queue(void) {}
 static inline bool ima_should_queue_key(void) { return false; }
 static inline bool ima_queue_key(struct key *keyring,
 				 const void *payload,
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 5d55ade5f3b9..195cb4079b2b 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -131,5 +131,11 @@ int __init ima_init(void)
 
 	ima_init_policy();
 
-	return ima_fs_init();
+	rc = ima_fs_init();
+	if (rc != 0)
+		return rc;
+
+	ima_init_key_queue();
+
+	return rc;
 }
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index 9b561f2b86db..c87c72299191 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/workqueue.h>
 #include <keys/asymmetric-type.h>
 #include "ima.h"
 
@@ -25,6 +26,36 @@ static bool ima_process_keys;
 static DEFINE_MUTEX(ima_keys_lock);
 static LIST_HEAD(ima_keys);
 
+/*
+ * If custom IMA policy is not loaded then keys queued up
+ * for measurement should be freed. This worker is used
+ * for handling this scenario.
+ */
+static long ima_key_queue_timeout = 300000; /* 5 Minutes */
+static void ima_keys_handler(struct work_struct *work);
+static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
+static bool timer_expired;
+
+/*
+ * This worker function frees keys that may still be
+ * queued up in case custom IMA policy was not loaded.
+ */
+static void ima_keys_handler(struct work_struct *work)
+{
+	timer_expired = true;
+	ima_process_queued_keys();
+}
+
+/*
+ * This function sets up a worker to free queued keys in case
+ * custom IMA policy was never loaded.
+ */
+void ima_init_key_queue(void)
+{
+	schedule_delayed_work(&ima_keys_delayed_work,
+			      msecs_to_jiffies(ima_key_queue_timeout));
+}
+
 static void ima_free_key_entry(struct ima_key_entry *entry)
 {
 	if (entry) {
@@ -119,13 +150,16 @@ void ima_process_queued_keys(void)
 	if (!process)
 		return;
 
+	if (!timer_expired)
+		cancel_delayed_work_sync(&ima_keys_delayed_work);
 
 	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
-		process_buffer_measurement(entry->payload,
-					   entry->payload_len,
-					   entry->keyring_name,
-					   KEY_CHECK, 0,
-					   entry->keyring_name);
+		if (!timer_expired)
+			process_buffer_measurement(entry->payload,
+						   entry->payload_len,
+						   entry->keyring_name,
+						   KEY_CHECK, 0,
+						   entry->keyring_name);
 		list_del(&entry->list);
 		ima_free_key_entry(entry);
 	}
-- 
2.17.1

Re: [PATCH v9 1/3] IMA: Define workqueue for early boot key measurements

[Mimi Zohar]

Hi Lakshmi,

On Wed, 2020-01-22 at 17:32 -0800, Lakshmi Ramasubramanian wrote:
> Measuring keys requires a custom IMA policy to be loaded.
> Keys created or updated before a custom IMA policy is loaded should
> be queued and the keys should be processed after a custom policy
> is loaded.

The addition of "and the keys" makes the sentence a run-on.  I've
reverted this change.

> 
> This patch defines workqueue for queuing keys when a custom IMA policy
> has not yet been loaded. An intermediate Kconfig boolean option namely
> IMA_QUEUE_EARLY_BOOT_KEYS is used to declare the workqueue functions.
> 
> A flag namely ima_process_keys is used to check if the key should be
> queued or should be processed immediately.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Thanks!  With this patch, if queueing keys ever becomes an issue,
resolving it will be straight forward.

This patch set is now in the next-integrity-testing branch.  Assuming
there are no problems, it will be merged into the next-integrity
branch, requiring a rebase.  I'm sorry for any inconvenience this may
cause.

Mimi

> ---
>  security/integrity/ima/Kconfig          |   5 +
>  security/integrity/ima/Makefile         |   1 +
>  security/integrity/ima/ima.h            |  22 ++++
>  security/integrity/ima/ima_queue_keys.c | 137 ++++++++++++++++++++++++
>  4 files changed, 165 insertions(+)
>  create mode 100644 security/integrity/ima/ima_queue_keys.c
> 
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 6bec78eeeae8..711ff10fa36e 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -317,3 +317,8 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
>  	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
>  	default y
>  
> +config IMA_QUEUE_EARLY_BOOT_KEYS
> +	bool
> +	depends on IMA_MEASURE_ASYMMETRIC_KEYS
> +	depends on SYSTEM_TRUSTED_KEYRING
> +	default y
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index 3e9d0ad68c7b..064a256f8725 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -13,3 +13,4 @@ ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
>  ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
>  obj-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
> +obj-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index f06238e41a7c..905ed2f7f778 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -205,6 +205,28 @@ extern const char *const func_tokens[];
>  
>  struct modsig;
>  
> +#ifdef CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS
> +/*
> + * To track keys that need to be measured.
> + */
> +struct ima_key_entry {
> +	struct list_head list;
> +	void *payload;
> +	size_t payload_len;
> +	char *keyring_name;
> +};
> +bool ima_should_queue_key(void);
> +bool ima_queue_key(struct key *keyring, const void *payload,
> +		   size_t payload_len);
> +void ima_process_queued_keys(void);
> +#else
> +static inline bool ima_should_queue_key(void) { return false; }
> +static inline bool ima_queue_key(struct key *keyring,
> +				 const void *payload,
> +				 size_t payload_len) { return false; }
> +static inline void ima_process_queued_keys(void) {}
> +#endif /* CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS */
> +
>  /* LIM API function definitions */
>  int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>  		   int mask, enum ima_hooks func, int *pcr,
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> new file mode 100644
> index 000000000000..9b561f2b86db
> --- /dev/null
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -0,0 +1,137 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2019 Microsoft Corporation
> + *
> + * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
> + *
> + * File: ima_queue_keys.c
> + *       Enables deferred processing of keys
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <keys/asymmetric-type.h>
> +#include "ima.h"
> +
> +/*
> + * Flag to indicate whether a key can be processed
> + * right away or should be queued for processing later.
> + */
> +static bool ima_process_keys;
> +
> +/*
> + * To synchronize access to the list of keys that need to be measured
> + */
> +static DEFINE_MUTEX(ima_keys_lock);
> +static LIST_HEAD(ima_keys);
> +
> +static void ima_free_key_entry(struct ima_key_entry *entry)
> +{
> +	if (entry) {
> +		kfree(entry->payload);
> +		kfree(entry->keyring_name);
> +		kfree(entry);
> +	}
> +}
> +
> +static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
> +						 const void *payload,
> +						 size_t payload_len)
> +{
> +	int rc = 0;
> +	struct ima_key_entry *entry;
> +
> +	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> +	if (entry) {
> +		entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
> +		entry->keyring_name = kstrdup(keyring->description,
> +					      GFP_KERNEL);
> +		entry->payload_len = payload_len;
> +	}
> +
> +	if ((entry == NULL) || (entry->payload == NULL) ||
> +	    (entry->keyring_name == NULL)) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	INIT_LIST_HEAD(&entry->list);
> +
> +out:
> +	if (rc) {
> +		ima_free_key_entry(entry);
> +		entry = NULL;
> +	}
> +
> +	return entry;
> +}
> +
> +bool ima_queue_key(struct key *keyring, const void *payload,
> +		   size_t payload_len)
> +{
> +	bool queued = false;
> +	struct ima_key_entry *entry;
> +
> +	entry = ima_alloc_key_entry(keyring, payload, payload_len);
> +	if (!entry)
> +		return false;
> +
> +	mutex_lock(&ima_keys_lock);
> +	if (!ima_process_keys) {
> +		list_add_tail(&entry->list, &ima_keys);
> +		queued = true;
> +	}
> +	mutex_unlock(&ima_keys_lock);
> +
> +	if (!queued)
> +		ima_free_key_entry(entry);
> +
> +	return queued;
> +}
> +
> +/*
> + * ima_process_queued_keys() - process keys queued for measurement
> + *
> + * This function sets ima_process_keys to true and processes queued keys.
> + * From here on keys will be processed right away (not queued).
> + */
> +void ima_process_queued_keys(void)
> +{
> +	struct ima_key_entry *entry, *tmp;
> +	bool process = false;
> +
> +	if (ima_process_keys)
> +		return;
> +
> +	/*
> +	 * Since ima_process_keys is set to true, any new key will be
> +	 * processed immediately and not be queued to ima_keys list.
> +	 * First one setting the ima_process_keys flag to true will
> +	 * process the queued keys.
> +	 */
> +	mutex_lock(&ima_keys_lock);
> +	if (!ima_process_keys) {
> +		ima_process_keys = true;
> +		process = true;
> +	}
> +	mutex_unlock(&ima_keys_lock);
> +
> +	if (!process)
> +		return;
> +
> +
> +	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
> +		process_buffer_measurement(entry->payload,
> +					   entry->payload_len,
> +					   entry->keyring_name,
> +					   KEY_CHECK, 0,
> +					   entry->keyring_name);
> +		list_del(&entry->list);
> +		ima_free_key_entry(entry);
> +	}
> +}
> +
> +inline bool ima_should_queue_key(void)
> +{
> +	return !ima_process_keys;
> +}