linux-kernel - Re: [PATCH v9 13/25] security: Introduce file

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Date: Wed, 07 Feb 2024 22:18:44 -0500
From: Paul Moore <paul@...l-moore.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, 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 13/25] security: Introduce file_release hook

On Jan 15, 2024 Roberto Sassu <roberto.sassu@...weicloud.com> wrote:
> 
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the file_release hook.
> 
> IMA calculates at file close the new digest of the file content and writes
> it to security.ima, so that appraisal at next file access succeeds.
> 
> An LSM could implement an exclusive access scheme for files, only allowing
> access to files that have no references.

Let's drop the above sentence as it is is a little vague and is causing
some concern with the VFS folks.  While I want to see the hooks explained
and documented in the code, I've never been a big fan of speculating
about potential future uses of the hook, that's dangerous IMO.

Otherwise this looks good.

Acked-by: Paul Moore <paul@...l-moore.com>

> The new hook cannot return an error and cannot cause the operation to be
> reverted.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
>  fs/file_table.c               |  1 +
>  include/linux/lsm_hook_defs.h |  1 +
>  include/linux/security.h      |  4 ++++
>  security/security.c           | 11 +++++++++++
>  4 files changed, 17 insertions(+)

--
paul-moore.com