linux-kernel - Re: [PATCH v9 16/23] ima: Implement ima_free_policy_rules() for freeing of an ima

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Date:   Fri, 28 Jan 2022 09:02:23 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org
Cc:     serge@...lyn.com, christian.brauner@...ntu.com,
        containers@...ts.linux.dev, dmitry.kasatkin@...il.com,
        ebiederm@...ssion.com, krzysztof.struczynski@...wei.com,
        roberto.sassu@...wei.com, mpeters@...hat.com, lhinds@...hat.com,
        lsturman@...hat.com, puiterwi@...hat.com, jejb@...ux.ibm.com,
        jamjoom@...ibm.com, linux-kernel@...r.kernel.org,
        paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: Re: [PATCH v9 16/23] ima: Implement ima_free_policy_rules() for
 freeing of an ima_namespace

Hi Stefan,

On Tue, 2022-01-25 at 17:46 -0500, Stefan Berger wrote:
> From: Stefan Berger <stefanb@...ux.ibm.com>
> 
> Implement ima_free_policy_rules() that is needed when an ima_namespace
> is freed.
> 
> Only reset temp_ima_appraise when using init_ima_ns.

Instead of having to walk the policy rules to know if there are any
"appraise" rules, the ima_appraise flag is set.  For now, only reset
temp_ima_appraise flag on failed policy rule updates for init_ima_ns.

> 
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
> 
> ---
>  v9:
>   - Only reset temp_ima_appraise when using init_ima_ns.
> ---
>  security/integrity/ima/ima.h        |  1 +
>  security/integrity/ima/ima_policy.c | 20 +++++++++++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index aea8fb8d2854..8c757223d549 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -329,6 +329,7 @@ void ima_update_policy_flags(struct ima_namespace *ns);
>  ssize_t ima_parse_add_rule(struct ima_namespace *ns, char *rule);
>  void ima_delete_rules(struct ima_namespace *ns);
>  int ima_check_policy(struct ima_namespace *ns);
> +void ima_free_policy_rules(struct ima_namespace *ns);
>  void *ima_policy_start(struct seq_file *m, loff_t *pos);
>  void *ima_policy_next(struct seq_file *m, void *v, loff_t *pos);
>  void ima_policy_stop(struct seq_file *m, void *v);
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index e8140e73d80b..47f2d1b5d156 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1880,13 +1880,31 @@ void ima_delete_rules(struct ima_namespace *ns)
>  {
>  	struct ima_rule_entry *entry, *tmp;
>  
> -	temp_ima_appraise = 0;
> +	if (ns == &init_ima_ns)
> +		temp_ima_appraise = 0;
> +
>  	list_for_each_entry_safe(entry, tmp, &ns->ima_temp_rules, list) {
>  		list_del(&entry->list);
>  		ima_free_rule(entry);
>  	}
>  }
>  
> +/**
> + * ima_free_policy_rules - free all policy rules
> + * @ns: IMA namespace that has the policy
> + */
> +void ima_free_policy_rules(struct ima_namespace *ns)
> +{
> +	struct ima_rule_entry *entry, *tmp;
> +
> +	ima_delete_rules(ns);

When the IMA policy is being extended, new rules are temporarily added
to the ima_temp_rules list.  If the entire set of rules being added are
valid, they're appended to the tail.

There shouldn't be any rules on the ima_temp_rules list unless the
policy is currently being extended.  Is that possible at this point?

> +
> +	list_for_each_entry_safe(entry, tmp, &ns->ima_policy_rules, list) {
> +		list_del(&entry->list);
> +		ima_free_rule(entry);
> +	}
> +}
> +
>  #define __ima_hook_stringify(func, str)	(#func),
>  
>  const char *const func_tokens[] = {

thanks,

Mimi