[PATCH v9 13/25] security: Introduce file_release hook

[Paul Moore]

On Jan 15, 2024 Roberto Sassu <roberto.sassu at 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 at 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 at 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(+)

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