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Subject[PATCH v1] IMA: Defined timer to free queued keys
Date
keys queued for measurement should still be processed even if
a custom IMA policy was not loaded. Otherwise, the keys will
remain queued forever consuming kernel memory.

This patch defines a timer to handle the above scenario. The timer
is setup to expire 5 minutes after IMA initialization is completed.

If a custom IMA policy is loaded before the timer expires, the timer
is removed and any queued keys are processed for measurement.
But if a custom policy was not loaded, on timer expiration
any queued keys are just freed.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
security/integrity/ima/ima.h | 2 +
security/integrity/ima/ima_asymmetric_keys.c | 46 ++++++++++++++++++--
security/integrity/ima/ima_init.c | 8 +++-
3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 97f8a4078483..c483215a9ee5 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -216,8 +216,10 @@ struct ima_key_entry {
char *keyring_name;
};
void ima_process_queued_keys(void);
+void ima_init_key_queue(void);
#else
static inline void ima_process_queued_keys(void) {}
+static inline void ima_init_key_queue(void) {}
#endif /* CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE */

/* LIM API function definitions */
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 4124f10ff0c2..e1c4e1e7d9a1 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -11,6 +11,7 @@

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/timer.h>
#include <keys/asymmetric-type.h>
#include "ima.h"

@@ -26,6 +27,34 @@ static bool ima_process_keys;
static DEFINE_MUTEX(ima_keys_mutex);
static LIST_HEAD(ima_keys);

+/*
+ * If custom IMA policy is not loaded then keys queued up
+ * for measurement should be freed. This timer is used
+ * for handling this scenario.
+ */
+static long ima_key_queue_timeout = 300000; /* 5 Minutes */
+static struct timer_list ima_key_queue_timer;
+
+/*
+ * This timer callback function processes keys that may still be
+ * queued up in case custom IMA policy was not loaded.
+ */
+static void ima_timer_handler(struct timer_list *timer)
+{
+ ima_process_queued_keys();
+}
+
+/*
+ * This function sets up a timer to process queued keys in case
+ * custom IMA policy was never loaded.
+ */
+void ima_init_key_queue(void)
+{
+ timer_setup(&ima_key_queue_timer, ima_timer_handler, 0);
+ mod_timer(&ima_key_queue_timer,
+ jiffies + msecs_to_jiffies(ima_key_queue_timeout));
+}
+
static void ima_free_key_entry(struct ima_key_entry *entry)
{
if (entry) {
@@ -100,6 +129,7 @@ void ima_process_queued_keys(void)
{
struct ima_key_entry *entry, *tmp;
bool process = false;
+ int timer_removed;

if (ima_process_keys)
return;
@@ -120,10 +150,20 @@ void ima_process_queued_keys(void)
if (!process)
return;

+ /*
+ * Timer is no longer needed. If the timer was removed
+ * (i.e., the timer had not expired) the queued keys are
+ * processed for measurement. Else, the keys are just freed.
+ */
+ timer_removed = del_timer(&ima_key_queue_timer);
+
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_removed)
+ 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);
}
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;
}
--
2.17.1
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