Re: [PATCH v12 10/26] ima: Switch to lazy lsm policy updates for better performance

Serge E. Hallyn
2022-05-22T17:06:50Z

On Wed, Apr 20, 2022 at 10:06:17AM -0400, Stefan Berger wrote:
> Instead of calling ima_lsm_update_rules() for every namespace upon
> invocation of the ima_lsm_policy_change() notification function,
> only set a flag in a namespace and defer the call to
> ima_lsm_update_rules() to before the policy is accessed the next time,
> which is either in ima_policy_start(), when displaying the policy via
> the policy file in securityfs, or when calling ima_match_policy().
>
> The performance numbers before this change for a test enabling
> and disabling an SELinux module was as follows with a given number
> of IMA namespaces that each a have a policy containing 2 rules
> with SELinux labels:
>
> 2: ~9s
> 192: ~11s
> 1920: ~80s
>
> With this change:
>
> 2: ~6.5s
> 192: ~7s
> 1920: ~8.3s
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

Acked-by: Serge Hallyn <serge@hallyn.com>

> ---
> security/integrity/ima/ima.h | 4 ++++
> security/integrity/ima/ima_policy.c | 15 ++++++++++++++-
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index c68b5117d034..5bf7f080c2be 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -123,6 +123,10 @@ struct ima_h_table {
> };
>
> struct ima_namespace {
> + unsigned long ima_ns_flags;
> +/* Bit numbers for above flags; use BIT() to get flag */
> +#define IMA_NS_LSM_UPDATE_RULES 0
> +
> /* policy rules */
> struct list_head ima_default_rules; /* Kconfig, builtin & arch rules */
> struct list_head ima_policy_rules; /* arch & custom rules */
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 23c559c8fae9..59e4ae5a6361 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -228,6 +228,14 @@ static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
> {.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
> };
>
> +static void ima_lsm_update_rules(struct ima_namespace *ns);
> +
> +static inline void ima_lazy_lsm_update_rules(struct ima_namespace *ns)
> +{
> + if (test_and_clear_bit(IMA_NS_LSM_UPDATE_RULES, &ns->ima_ns_flags))
> + ima_lsm_update_rules(ns);
> +}
> +
> static int ima_policy __initdata;
>
> static int __init default_measure_policy_setup(char *str)
> @@ -478,7 +486,8 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
> return NOTIFY_DONE;
>
> ns = container_of(nb, struct ima_namespace, ima_lsm_policy_notifier);
> - ima_lsm_update_rules(ns);
> +
> + set_bit(IMA_NS_LSM_UPDATE_RULES, &ns->ima_ns_flags);
>
> return NOTIFY_OK;
> }
> @@ -705,6 +714,8 @@ int ima_match_policy(struct ima_namespace *ns,
> if (template_desc && !*template_desc)
> *template_desc = ima_template_desc_current();
>
> + ima_lazy_lsm_update_rules(ns);
> +
> rcu_read_lock();
> ima_rules_tmp = rcu_dereference(ns->ima_rules);
> list_for_each_entry_rcu(entry, ima_rules_tmp, list) {
> @@ -1907,6 +1918,8 @@ void *ima_policy_start(struct seq_file *m, loff_t *pos)
> struct ima_rule_entry *entry;
> struct list_head *ima_rules_tmp;
>
> + ima_lazy_lsm_update_rules(ns);
> +
> rcu_read_lock();
> ima_rules_tmp = rcu_dereference(ns->ima_rules);
> list_for_each_entry_rcu(entry, ima_rules_tmp, list) {
> --
> 2.34.1