[PATCH v5 15/23] security: Introduce inode_post_create_tmpfile hook

[Paul Moore]

On Nov  7, 2023 Roberto Sassu <roberto.sassu at huaweicloud.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 at huawei.com>
> Acked-by: Casey Schaufler <casey at schaufler-ca.com>
> Reviewed-by: Mimi Zohar <zohar at linux.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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