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SubjectRe: [PATCH v2] IMA: Defined timer to free queued keys
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On Tue, 2019-12-24 at 10:01 -0800, Lakshmi Ramasubramanian wrote:
> 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 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
> queued keys are just freed.
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Thanks.  This patch is now queued in next-integrity-testing.

Mimi

> ---
> security/integrity/ima/ima.h | 2 +
> security/integrity/ima/ima_asymmetric_keys.c | 42 ++++++++++++++++++--
> security/integrity/ima/ima_init.c | 8 +++-
> 3 files changed, 48 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..9ea2233c911a 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 +27,36 @@ 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;
> +static bool timer_expired;
> +
> +/*
> + * This timer callback 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)
> +{
> + timer_expired = true;
> + ima_process_queued_keys();
> +}
> +
> +/*
> + * This function sets up a timer 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));
> +}
> +
> static void ima_free_key_entry(struct ima_key_entry *entry)
> {
> if (entry) {
> @@ -120,10 +151,15 @@ void ima_process_queued_keys(void)
> if (!process)
> return;
>
> + 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_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);
> }
> 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;
> }

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