linux-kernel - Re: [PATCH v9 08/23] ima: Move measurement list related variables into ima

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Date:   Wed, 26 Jan 2022 17:23:49 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Christian Brauner <brauner@...nel.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        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 v9 08/23] ima: Move measurement list related variables
 into ima_namespace


On 1/26/22 04:21, Christian Brauner wrote:
> On Tue, Jan 25, 2022 at 05:46:30PM -0500, Stefan Berger wrote:
>> From: Stefan Berger <stefanb@...ux.ibm.com>
>>
>> Move measurement list related variables into the ima_namespace. This way
>> a front-end like securityfs can show the measurement list inside an IMA
>> namespace.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> ---
>>   security/integrity/ima/ima.h             |  5 +++--
>>   security/integrity/ima/ima_fs.c          |  6 ++++--
>>   security/integrity/ima/ima_init_ima_ns.c |  5 +++++
>>   security/integrity/ima/ima_kexec.c       | 12 ++++++-----
>>   security/integrity/ima/ima_queue.c       | 27 +++++++++++-------------
>>   5 files changed, 31 insertions(+), 24 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index 340a59174670..45706836a77b 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -106,7 +106,6 @@ struct ima_queue_entry {
>>   	struct list_head later;		/* place in ima_measurements list */
>>   	struct ima_template_entry *entry;
>>   };
>> -extern struct list_head ima_measurements;	/* list of all measurements */
>>   
>>   /* Some details preceding the binary serialized measurement list */
>>   struct ima_kexec_hdr {
>> @@ -136,6 +135,8 @@ struct ima_namespace {
>>   	struct ima_rule_entry *arch_policy_entry;
>>   
>>   	struct ima_h_table ima_htable;
>> +	struct list_head ima_measurements;	/* list of all measurements */
>> +	unsigned long binary_runtime_size;	/* used by init_ima_ns */
>>   } __randomize_layout;
> Moving this into struct imans seems sane to me but I'm not going to ack
> it because I don't have enough knowledge to guarantee that this code
> will only run for init_ima_ns. I'll leave that to Mimi.

The code modifying binary_runtime_size may do this for all IMA 
namespaces but the resulting value of binary_runtime_size may only 
matter in init_ima_ns (not 100% sure, but Mimi seems to say so). Moving 
it into ima_namespace rather than special-casing the code keeps the code 
readable.

There are also some case in the code that may do something like this:

if (ns == &init_ima_ns)

     foo = xyz;

Those will go away when foo is moved into the namespace and then it 
becomes ns->foo = xyz, which is much saner for readability but 
unavoidable for some variables at this stage.