Received-SPF: pass (google.com: domain of linux-kernel+bounces-57422-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Wed, 07 Feb 2024 22:18:44 -0500
Message-ID: <77e42fa37a24378fbb4f19ee9a4d2e74@paul-moore.com>
Precedence: bulk
MIME-Version: 1.0 
Content-Type: text/plain; charset=utf-8 
Content-Disposition: inline 
Content-Transfer-Encoding: 8bit
From: Paul Moore <paul@paul-moore.com>
To: Roberto Sassu <roberto.sassu@huaweicloud.com>, viro@zeniv.linux.org.uk, brauner@kernel.org, chuck.lever@oracle.com, jlayton@kernel.org, neilb@suse.de, kolga@netapp.com, Dai.Ngo@oracle.com, tom@talpey.com, jmorris@namei.org, serge@hallyn.com, zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, dhowells@redhat.com, jarkko@kernel.org, stephen.smalley.work@gmail.com, eparis@parisplace.org, casey@schaufler-ca.com, shuah@kernel.org, mic@digikod.net
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, selinux@vger.kernel.org, linux-kselftest@vger.kernel.org, Roberto Sassu <roberto.sassu@huawei.com>
Subject: Re: [PATCH v9 13/25] security: Introduce file_release hook
References: <20240115181809.885385-14-roberto.sassu@huaweicloud.com>
In-Reply-To: <20240115181809.885385-14-roberto.sassu@huaweicloud.com>

On Jan 15, 2024 Roberto Sassu <roberto.sassu@huaweicloud.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@paul-moore.com>

> The new hook cannot return an error and cannot cause the operation to be
> reverted.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.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