linux-kernel - Re: [PATCH-v2 3/6] ima: added ima_get_template_desc() for templates dynamic registration

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Date:	Mon, 09 Dec 2013 08:35:32 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Roberto Sassu <roberto.sassu@...ito.it>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net, zohar@...ibm.com,
	d.kasatkin@...sung.com, james.l.morris@...cle.com
Subject: Re: [PATCH-v2 3/6] ima: added ima_get_template_desc() for templates
 dynamic registration

On Tue, 2013-11-19 at 13:33 +0100, Roberto Sassu wrote: 
> This patch introduces the ima_get_template_desc() function which returns
> a template descriptor depending on the template name and format passed
> as arguments (at least one argument should be not NULL). If the first
> argument is not NULL, the new function searches an existing template
> descriptor by name among those defined and returns it to the caller.
> Instead, if the second argument is not NULL and the first is NULL,
> it does a template lookup by format and, if not found, creates a new one
> before returning the pointer to the caller. Newly created templates
> are cached to avoid duplicates.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>
> ---
>  security/integrity/ima/ima.h          |  2 ++
>  security/integrity/ima/ima_template.c | 45 +++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 8b4a4f3..632d92e 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -109,6 +109,8 @@ int ima_init_crypto(void);
>  void ima_putc(struct seq_file *m, void *data, int datalen);
>  void ima_print_digest(struct seq_file *m, u8 *digest, int size);
>  struct ima_template_desc *ima_template_desc_current(void);
> +struct ima_template_desc *ima_get_template_desc(char *template_name,
> +						char *template_fmt);
>  int ima_init_template(void);
> 
>  int ima_init_template(void);
> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> index c849723..9bec7d4 100644
> --- a/security/integrity/ima/ima_template.c
> +++ b/security/integrity/ima/ima_template.c
> @@ -41,6 +41,8 @@ static struct ima_template_desc *ima_template;
>  static struct ima_template_desc *lookup_template_desc_by_name(const char *name);
>  static struct ima_template_field *lookup_template_field(const char *field_id);
> 
> +static DEFINE_MUTEX(ima_templates_mutex);
> +
>  static int __init ima_template_setup(char *str)
>  {
>  	struct ima_template_desc *template_desc;
> @@ -248,6 +250,49 @@ struct ima_template_desc *ima_template_desc_current(void)
>  	return ima_template;
>  }
> 
> +struct ima_template_desc *ima_get_template_desc(char *template_name,
> +						char *template_fmt)
> +{
> +	struct ima_template_desc *desc;
> +	int result;
> +
> +	if (template_name == NULL && template_fmt == NULL)
> +		return NULL;

Originally, before using a variable, we checked that it wasn't NULL.
This changed, at some point. (Can someone supply a reference, please?)
As the only code calling ima_get_template_desc() will be IMA, this check
shouldn't be required.

> +
> +	if (template_name)
> +		desc = lookup_template_desc_by_name(template_name);
> +	else {
> +		mutex_lock(&ima_templates_mutex);
> +		desc = lookup_template_desc_by_fmt(template_fmt);
> +		if (desc == NULL) {
> +			desc = kzalloc(sizeof(*desc), GFP_KERNEL);
> +			if (desc == NULL)
> +				goto out_unlock;
> +		}
> +		desc->name = "";

What's this?

> +		desc->fmt = kstrdup(template_fmt, GFP_KERNEL);
> +		if (desc->fmt == NULL)
> +			goto out_free;
> +
> +		result = template_desc_init_fields(desc->fmt, &(desc->fields),
> +						   &(desc->num_fields));
> +		if (result < 0)
> +			goto out_free_fmt;
> +

This patch set was posted before the new cleanup functions were defined.
Reminder, to use your new cleanup function.

> +		list_add_tail(&desc->list, &defined_templates[0].list);
> +		mutex_unlock(&ima_templates_mutex);

Right, as new template formats can only be added, not deleted, locking
just here, to prevent duplicates, should be fine.  Perhaps add a short
comment, indicating this is safe, because templates are not ever
removed.

thanks,

Mimi

> +	}
> +
> +	return desc;
> +out_free_fmt:
> +	kfree(desc->fmt);
> +out_free:
> +	kfree(desc);
> +out_unlock:
> +	mutex_unlock(&ima_templates_mutex);
> +	return NULL;
> +}
> +
>  int ima_init_template(void)
>  {
>  	int result;


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