linux-kernel - Re: [PATCH v8 03/19] ima: Move policy related variables into ima

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Date:   Thu, 13 Jan 2022 15:26:51 -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 v8 03/19] ima: Move policy related variables into
 ima_namespace

Hi Stefan,

On Tue, 2022-01-04 at 12:04 -0500, Stefan Berger wrote:
> From: Stefan Berger <stefanb@...ux.ibm.com>
> 
> Move variables related to the IMA policy into the ima_namespace. This way
> the IMA policy of an IMA namespace can be set and displayed using a
> front-end like SecurityFS.
> 
> Implement ima_ns_from_file() to get the IMA namespace via the user
> namespace of the SecurityFS superblock that a file belongs to.
> 
> To get the current ima_namespace use get_current_ns() when a function
> that is related to a policy rule is called. In other cases where functions
> are called due file attribute modifications, use init_ima_ns, since these
> functions are related to IMA appraisal and changes to file attributes are
> only relevant to the init_ima_ns until IMA namespaces also support IMA
> appraisal. In ima_file_free() use init_ima_ns since in this case flags
> related to file measurements may be affected, which is not supported in
> IMA namespaces, yet.
> 
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>

Please split this patch into "ima: pass through ima namespace", or some
other name,  and "ima: Move policy related variables into
ima_namespace".  The other option is to combine the "pass through ima
namespace" with the 2nd patch, like Christian's example.

> ---
>  security/integrity/ima/ima.h                 |  49 ++++---
>  security/integrity/ima/ima_api.c             |   8 +-
>  security/integrity/ima/ima_appraise.c        |  28 ++--
>  security/integrity/ima/ima_asymmetric_keys.c |   4 +-
>  security/integrity/ima/ima_fs.c              |  16 ++-
>  security/integrity/ima/ima_init.c            |   8 +-
>  security/integrity/ima/ima_init_ima_ns.c     |   6 +
>  security/integrity/ima/ima_main.c            |  83 +++++++----
>  security/integrity/ima/ima_policy.c          | 142 ++++++++++---------
>  security/integrity/ima/ima_queue_keys.c      |  11 +-
>  10 files changed, 213 insertions(+), 142 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index c4af3275f015..0b3dc9425076 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -20,6 +20,7 @@
>  #include <linux/hash.h>
>  #include <linux/tpm.h>
>  #include <linux/audit.h>
> +#include <linux/user_namespace.h>
>  #include <crypto/hash_info.h>
>  
>  #include "../integrity.h"
> @@ -43,9 +44,6 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 };
>  
>  #define NR_BANKS(chip) ((chip != NULL) ? chip->nr_allocated_banks : 0)
>  
> -/* current content of the policy */
> -extern int ima_policy_flag;
> -
>  /* bitset of digests algorithms allowed in the setxattr hook */
>  extern atomic_t ima_setxattr_allowed_hash_algorithms;
>  
> @@ -120,6 +118,14 @@ struct ima_kexec_hdr {
>  };
>  
>  struct ima_namespace {
> +	struct list_head ima_default_rules;
> +	/* ns's policy rules */

Thank you for adding comments.  Why is the ima_default_rules not
considered "ns's policy rules"?   Will this come later or is it limited
to init_ima_ns?

> +	struct list_head ima_policy_rules;
> +	struct list_head ima_temp_rules;
> +	/* Pointer to ns's current policy */
> +	struct list_head __rcu *ima_rules;

Since "Pointer to ns's current policy" only refers to ima_rules, append
it to the variable definition.

> +	/* current content of the policy */
> +	int ima_policy_flag;

Similarly here append the comment to the variable definition.

>  } __randomize_layout;
>  extern struct ima_namespace init_ima_ns;

thanks,

Mimi