linux-kernel - Re: [PATCH v5 15/23] security: Introduce inode_post_create

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Message-ID: <9239b0744e5c9a006dd4fe88c8cdc41b.paul@paul-moore.com>
Date:   Wed, 15 Nov 2023 23:33:48 -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, 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>
Subject: Re: [PATCH v5 15/23] security: Introduce inode_post_create_tmpfile  hook

On Nov  7, 2023 Roberto Sassu <roberto.sassu@...weicloud.com> wrote:
> 
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_create_tmpfile hook.
> 
> As temp files can be made persistent, treat new temp files like other new
> files, so that the file hash is calculated and stored in the security
> xattr.
> 
> LSMs could also take some action after temp files have been created.
> 
> The new hook cannot return an error and cannot cause the operation to be
> canceled.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> ---
>  fs/namei.c                    |  1 +
>  include/linux/lsm_hook_defs.h |  2 ++
>  include/linux/security.h      |  6 ++++++
>  security/security.c           | 15 +++++++++++++++
>  4 files changed, 24 insertions(+)

...

> diff --git a/security/security.c b/security/security.c
> index 5eaf5f2aa5ea..ca650c285fd9 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2013,6 +2013,21 @@ int security_inode_create(struct inode *dir, struct dentry *dentry,
>  }
>  EXPORT_SYMBOL_GPL(security_inode_create);
>  
> +/**
> + * security_inode_post_create_tmpfile() - Update inode security of new tmpfile
> + * @idmap: idmap of the mount
> + * @inode: inode of the new tmpfile
> + *
> + * Update inode security data after a tmpfile has been created.
> + */
> +void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
> +					struct inode *inode)
> +{
> +	if (unlikely(IS_PRIVATE(inode)))
> +		return;

See my previous comments/questions about checking for S_PRIVATE here.

> +	call_void_hook(inode_post_create_tmpfile, idmap, inode);
> +}
> +
>  /**
>   * security_inode_link() - Check if creating a hard link is allowed
>   * @old_dentry: existing file
> -- 
> 2.34.1

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