Hi Lackshmi,
In the subject line and the patch description please refer to the
construct as "delayed workqueue" or even abbreviated as "delayed wq",
even though the struct itself is named "delayed_work.
On Tue, 2020-01-21 at 09:28 -0800, Lakshmi Ramasubramanian wrote:
> A timer is used to free queued keys if a custom IMA policy is not
^to free the queued keys,
> loaded within 5 minutes after IMA subsystem is initialized. Timer
^after the IMA subsystem
^The timer handler
> 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 <nramas@xxxxxxxxxxxxxxxxxxx>
> Fixes: 8f5d2d06f217 ("IMA: Defined timer to free queued keys")
Thank you. This is definitely better.
Mimi
> ---
> 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;
> ima_process_queued_keys();
> }
>
> /*
> - * 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)
> ima_free_key_entry(entry);
> @@ -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)
> return;
> @@ -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)
> return;
>
> - 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)
