linux-kernel - Re: [PATCH v9 24/25] ima: Make it independent from 'integrity' LSM

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Date: Mon, 12 Feb 2024 14:47:20 -0500
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>, viro@...iv.linux.org.uk,
        brauner@...nel.org, chuck.lever@...cle.com, jlayton@...nel.org,
        neilb@...e.de, kolga@...app.com, Dai.Ngo@...cle.com, tom@...pey.com,
        paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com,
        zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
        eric.snowberg@...cle.com, dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        casey@...aufler-ca.com, shuah@...nel.org, mic@...ikod.net
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        selinux@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v9 24/25] ima: Make it independent from 'integrity' LSM



On 1/15/24 13:18, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.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.
> 
> Create ima_iint.c and introduce the same integrity metadata management
> functions found in iint.c (renamed with ima_). However, instead of putting
> metadata in an rbtree, reserve space from IMA in the inode security blob
> for a pointer, and introduce the ima_inode_set_iint()/ima_inode_get_iint()
> primitives to store/retrieve that pointer. This improves search time from
> logarithm to constant.

logarithmic

> 
> Consequently, 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().
> 
> Prefer storing the pointer instead of the entire ima_iint_cache structure,
> to avoid too much memory pressure. Use the same mechanism as before, a
> cache named ima_iint_cache (renamed from iint_cache), to quickly allocate
> a new ima_iint_cache structure when requested by the IMA policy.
> 
> Create the new ima_iint_cache in ima_iintcache_init(),
> called by init_ima_lsm(), during the initialization of the 'ima' LSM. And,
> register ima_inode_free_security() to free the ima_iint_cache structure, if
> exists.
> 
> Replace integrity_iint_cache with ima_iint_cache in various places of the
> IMA code. Also, replace integrity_inode_get() and integrity_iint_find(),
> respectively with ima_inode_get() and ima_iint_find().
> 
> Finally, move the remaining IMA-specific flags
> to security/integrity/ima/ima.h, since they are now unnecessary in the
> common integrity layer.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>