linux-kernel - Re: [PATCH v10 16/27] ima: Implement ima_free_policy_rules() for freeing of an ima

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Message-ID: <55c0c300-3fe4-f610-0b78-adc5593a70a0@linux.ibm.com>
Date:   Fri, 18 Feb 2022 14:38:33 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Mimi Zohar <zohar@...ux.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
Subject: Re: [PATCH v10 16/27] ima: Implement ima_free_policy_rules() for
 freeing of an ima_namespace


On 2/18/22 12:09, Mimi Zohar wrote:
> On Tue, 2022-02-01 at 15:37 -0500, Stefan Berger wrote:
>> Implement ima_free_policy_rules() that is needed when an ima_namespace
>> is freed.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>>
>> ---
>> v10:
>>    - Not calling ima_delete_rules() anymore
>>    - Move access check from ima_delete_rules into very last patch
>>
>>   v9:
>>    - Only reset temp_ima_appraise when using init_ima_ns.
>> ---
>>   security/integrity/ima/ima.h        |  1 +
>>   security/integrity/ima/ima_policy.c | 14 ++++++++++++++
>>   2 files changed, 15 insertions(+)
>>
>> 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 2dcc5a8c585a..fe3dce8fb939 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -1889,6 +1889,20 @@ void ima_delete_rules(struct ima_namespace *ns)
>>   	}
>>   }
>>   
>> +/**
>> + * 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;
>> +
>> +	list_for_each_entry_safe(entry, tmp, &ns->ima_policy_rules, list) {
>> +		list_del(&entry->list);
>> +		ima_free_rule(entry);
>> +	}
>> +}
>> +
> The first time a policy is loaded, the policy rules pivot
> from ima_default_rules to the custom rules.  When this happens, the
> architecture specific policy rules are freed.  Here too, if a custom
> policy isn't already loaded, the architecture specific rules stored as
> an array need to be freed.  Refer to the comment in
> ima_update_policy().

Right. So here's how it's done (before arch_policy_entry was moved into 
ima_namespace).

         /*
          * IMA architecture specific policy rules are specified
          * as strings and converted to an array of ima_entry_rules
          * on boot.  After loading a custom policy, free the
          * architecture specific rules stored as an array.
          */
         kfree(arch_policy_entry);


So, I now added kfree(ns->arch_policy_entry).

Thanks.

    Stefan

>
>>   #define __ima_hook_stringify(func, str)	(#func),
>>   
>>   const char *const func_tokens[] = {