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From: Lakshmi Ramasubramanian <>
Subject: [PATCH] IMA: Use delayed work to free queued keys
Date: Tue, 21 Jan 2020 09:28:29 -0800	[thread overview]
Message-ID: <> (raw)

A timer is used to free queued keys if a custom IMA policy is not
loaded within 5 minutes after IMA subsystem is initialized. Timer
handler is called in interrupt context. Due to this a spinlock has
to be used to synchronize access to critical section. A mutex cannot
be used since a mutex can sleep.

This patch uses a delayed work to free queued keys. Since a delayed
work handler is called in process context a mutex can be used.

Signed-off-by: Lakshmi Ramasubramanian <>
Fixes: 8f5d2d06f217 ("IMA: Defined timer to free queued keys")
 security/integrity/ima/ima_asymmetric_keys.c | 33 ++++++++++----------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 381f51708e7b..fa1bdd54a9ff 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -11,7 +11,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#include <linux/timer.h>
+#include <linux/workqueue.h>
 #include <keys/asymmetric-type.h>
 #include "ima.h"
@@ -24,37 +24,37 @@ static bool ima_process_keys;
  * To synchronize access to the list of keys that need to be measured
-static DEFINE_SPINLOCK(ima_keys_lock);
+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 timer is used
+ * for measurement should be freed. This worker is used
  * for handling this scenario.
 static long ima_key_queue_timeout = 300000; /* 5 Minutes */
-static struct timer_list ima_key_queue_timer;
+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 timer callback function frees keys that may still be
+ * This worker function frees keys that may still be
  * queued up in case custom IMA policy was not loaded.
-static void ima_timer_handler(struct timer_list *timer)
+static void ima_keys_handler(struct work_struct *work)
 	timer_expired = true;
- * This function sets up a timer to free queued keys in case
+ * This function sets up a worker to free 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));
+	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)
@@ -103,18 +103,17 @@ static bool ima_queue_key(struct key *keyring, const void *payload,
 	bool queued = false;
 	struct ima_key_entry *entry;
-	unsigned long flags;
 	entry = ima_alloc_key_entry(keyring, payload, payload_len);
 	if (!entry)
 		return false;
-	spin_lock_irqsave(&ima_keys_lock, flags);
+	mutex_lock(&ima_keys_lock);
 	if (!ima_process_keys) {
 		list_add_tail(&entry->list, &ima_keys);
 		queued = true;
-	spin_unlock_irqrestore(&ima_keys_lock, flags);
+	mutex_unlock(&ima_keys_lock);
 	if (!queued)
@@ -132,7 +131,6 @@ void ima_process_queued_keys(void)
 	struct ima_key_entry *entry, *tmp;
 	bool process = false;
-	unsigned long flags;
 	if (ima_process_keys)
@@ -143,17 +141,18 @@ void ima_process_queued_keys(void)
 	 * First one setting the ima_process_keys flag to true will
 	 * process the queued keys.
-	spin_lock_irqsave(&ima_keys_lock, flags);
+	mutex_lock(&ima_keys_lock);
 	if (!ima_process_keys) {
 		ima_process_keys = true;
 		process = true;
-	spin_unlock_irqrestore(&ima_keys_lock, flags);
+	mutex_unlock(&ima_keys_lock);
 	if (!process)
-	del_timer(&ima_key_queue_timer);
+	if (!timer_expired)
+		cancel_delayed_work_sync(&ima_keys_delayed_work);
 	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
 		if (!timer_expired)

             reply	other threads:[~2020-01-21 17:28 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-21 17:28 Lakshmi Ramasubramanian [this message]
2020-01-22  2:39 ` [PATCH] IMA: Use delayed work to free queued keys Mimi Zohar

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