linux-kernel - Re: [PATCH v9 20/25] ima: Move to LSM infrastructure

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Date: Fri, 9 Feb 2024 10:50:05 +0100
From: Christian Brauner <brauner@...nel.org>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
Cc: viro@...iv.linux.org.uk, 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, 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 20/25] ima: Move to LSM infrastructure

On Mon, Jan 15, 2024 at 07:18:04PM +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
> 
> Move hardcoded IMA function calls (not appraisal-specific functions) from
> various places in the kernel to the LSM infrastructure, by introducing a
> new LSM named 'ima' (at the end of the LSM list and always enabled like
> 'integrity').
> 
> Having IMA before EVM in the Makefile is sufficient to preserve the
> relative order of the new 'ima' LSM in respect to the upcoming 'evm' LSM,
> and thus the order of IMA and EVM function calls as when they were
> hardcoded.
> 
> Make moved functions as static (except ima_post_key_create_or_update(),
> which is not in ima_main.c), and register them as implementation of the
> respective hooks in the new function init_ima_lsm().
> 
> Select CONFIG_SECURITY_PATH, to ensure that the path-based LSM hook
> path_post_mknod is always available and ima_post_path_mknod() is always
> executed to mark files as new, as before the move.
> 
> A slight difference is that IMA and EVM functions registered for the
> inode_post_setattr, inode_post_removexattr, path_post_mknod,
> inode_post_create_tmpfile, inode_post_set_acl and inode_post_remove_acl
> won't be executed for private inodes. Since those inodes are supposed to be
> fs-internal, they should not be of interest of IMA or EVM. The S_PRIVATE
> flag is used for anonymous inodes, hugetlbfs, reiserfs xattrs, XFS scrub
> and kernel-internal tmpfs files.
> 
> Conditionally register ima_post_key_create_or_update() if
> CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. Also, conditionally register
> ima_kernel_module_request() if CONFIG_INTEGRITY_ASYMMETRIC_KEYS is enabled.
> 
> Finally, add the LSM_ID_IMA case in lsm_list_modules_test.c.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> Acked-by: Chuck Lever <chuck.lever@...cle.com>
> ---
>  fs/file_table.c                               |   2 -
>  fs/namei.c                                    |   6 -
>  fs/nfsd/vfs.c                                 |   7 --
>  fs/open.c                                     |   1 -

Acked-by: Christian Brauner <brauner@...nel.org>