linux-kernel - Re: [PATCH v4 12/23] security: Introduce file_post

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Message-ID: <980b8df5eccc03a67328e28b7cef2b777bc310f0.camel@linux.ibm.com>
Date:   Mon, 06 Nov 2023 11:40:08 -0500
From:   Mimi Zohar <zohar@...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,
        dmitry.kasatkin@...il.com, dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        casey@...aufler-ca.com, mic@...ikod.net
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...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, Roberto Sassu <roberto.sassu@...wei.com>,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: Re: [PATCH v4 12/23] security: Introduce file_post_open hook

On Fri, 2023-10-27 at 10:35 +0200, Roberto Sassu wrote:
> diff --git a/security/security.c b/security/security.c
> index 2ee958afaf40..d24a8f92d641 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2947,6 +2947,23 @@ int security_file_open(struct file *file)
>         return fsnotify_perm(file, MAY_OPEN);
>  }
>  
> +/**
> + * security_file_post_open() - Recheck access to a file after it has been opened
> + * @file: the file
> + * @mask: access mask
> + *
> + * Recheck access with mask after the file has been opened. The hook is useful
> + * for LSMs that require the file content to be available in order to make
> + * decisions.
> + *

The hook isn't limited to "Recheck access".    It's used for measuring,
appraising, and auditing a file's integrity.   Sorry for suggesting an
incomplete patch description.  Please update the wording here and the
patch description accordingly.

> + * Return: Returns 0 if permission is granted.
> + */
> +int security_file_post_open(struct file *file, int mask)
> +{
> +       return call_int_hook(file_post_open, 0, file, mask);
> +}
> +EXPORT_SYMBOL_GPL(security_file_post_open);
> +
>  /**
>   * security_file_truncate() - Check if truncating a file is allowed
>   * @file: file

-- 
thanks,

Mimi