Re: [PATCH v8 23/24] ima: Make it independent from 'integrity' LSM

[Roberto Sassu <roberto.sassu@huaweicloud.com>]

On 12/27/2023 8:21 PM, Mimi Zohar wrote:
> On Wed, 2023-12-27 at 17:39 +0100, Roberto Sassu wrote:
>> On 12/27/2023 2:22 PM, Mimi Zohar wrote:
>>> On Thu, 2023-12-14 at 18:08 +0100, Roberto Sassu wrote:
>>>> From: Roberto Sassu <roberto.sassu@huawei.com>
>>>>
>>>> Make the 'ima' LSM independent from the 'integrity' LSM by introducing IMA
>>>> own integrity metadata (ima_iint_cache structure, with IMA-specific fields
>>>> from the integrity_iint_cache structure), and by managing it directly from
>>>> the 'ima' LSM.
>>>>
>>>> Move the remaining IMA-specific flags to security/integrity/ima/ima.h,
>>>> since they are now unnecessary in the common integrity layer.
>>>>
>>>> Replace integrity_iint_cache with ima_iint_cache in various places
>>>> of the IMA code.
>>>>
>>>> Then, reserve space in the security blob for the entire ima_iint_cache
>>>> structure, so that it is available for all inodes having the security blob
>>>> allocated (those for which security_inode_alloc() was called).  Adjust the
>>>> IMA code accordingly, call ima_iint_inode() to retrieve the ima_iint_cache
>>>> structure. Keep the non-NULL checks since there can be inodes without
>>>> security blob.
>>>
>>> Previously the 'iint' memory was only allocated for regular files in
>>> policy and were tagged S_IMA.  This patch totally changes when and how
>>> memory is being allocated.  Does it make sense to allocate memory at
>>> security_inode_alloc()?  Is this change really necessary for making IMA
>>> a full fledged LSM?
>>
>> Good question. I think it wouldn't be necessary, we can reuse the same
>> approach as in the patch 'integrity: Switch from rbtree to LSM-managed
>> blob for integrity_iint_cache'.
> 
> Going forward with the v8 proposed solution would require some real
> memory usage analysis for different types of policies.
> 
> To me the "integrity: Switch from rbtree to LSM-managed blob for
> integrity_iint_cache" makes a lot more sense.   Looking back at the
> original thread, your reasons back then for not directly allocating the
> integrity_iint_cache are still valid for the ima_iint_cache structure.

Uhm, ok. It should not be too difficult to restore the old mechanism for 
ima_iint_cache. Will do it in v9.

Thanks

Roberto

> Mimi
> 
>>>
>>>>
>>>> Don't include the inode pointer as field in the ima_iint_cache structure,
>>>> since the association with the inode is clear. Since the inode field is
>>>> missing in ima_iint_cache, pass the extra inode parameter to
>>>> ima_get_verity_digest().
>>>>
>>>> Finally, register ima_inode_alloc_security/ima_inode_free_security() to
>>>> initialize/deinitialize the new ima_iint_cache structure (before this task
>>>> was done by iint_init_always() and iint_free()). Also, duplicate
>>>> iint_lockdep_annotate() for the ima_iint_cache structure, and name it
>>>> ima_iint_lockdep_annotate().
>>>>
>>>> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
>>
>