ima: Allow template selection with ima_template[_fmt]= after ima_hash=

Commit c2426d2 ("ima: added support for new kernel cmdline parameter
ima_template_fmt") introduced an additional check on the ima_template
variable to avoid multiple template selection.

Unfortunately, ima_template could be also set by the setup function of the
ima_hash= parameter, when it calls ima_template_desc_current(). This causes
attempts to choose a new template with ima_template= or with
ima_template_fmt=, after ima_hash=, to be ignored.

Achieve the goal of the commit mentioned with the new static variable
template_setup_done, so that template selection requests after ima_hash=
are not ignored.

Finally, call ima_init_template_list(), if not already done, to initialize
the list of templates before lookup_template_desc() is called.

Reported-by: Guo Zihua <guozihua@huawei.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Cc: stable@vger.kernel.org
Fixes: c2426d2 ("ima: added support for new kernel cmdline parameter ima_template_fmt")
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Author: robertosassu

security/integrity/ima/ima_template.c

@@ -29,6 +29,7 @@ static struct ima_template_desc builtin_templates[] = {
 
 static LIST_HEAD(defined_templates);
 static DEFINE_SPINLOCK(template_list);
+static int template_setup_done;
 
 static const struct ima_template_field supported_fields[] = {
 	{.field_id = "d", .field_init = ima_eventdigest_init,
@@ -101,10 +102,11 @@ static int __init ima_template_setup(char *str)
 	struct ima_template_desc *template_desc;
 	int template_len = strlen(str);
 
-	if (ima_template)
+	if (template_setup_done)
 		return 1;
 
-	ima_init_template_list();
+	if (!ima_template)
+		ima_init_template_list();
 
 	/*
 	 * Verify that a template with the supplied name exists.
@@ -128,6 +130,7 @@ static int __init ima_template_setup(char *str)
 	}
 
 	ima_template = template_desc;
+	template_setup_done = 1;
 	return 1;
 }
 __setup("ima_template=", ima_template_setup);
@@ -136,7 +139,7 @@ static int __init ima_template_fmt_setup(char *str)
 {
 	int num_templates = ARRAY_SIZE(builtin_templates);
 
-	if (ima_template)
+	if (template_setup_done)
 		return 1;
 
 	if (template_desc_init_fields(str, NULL, NULL) < 0) {
@@ -147,6 +150,7 @@ static int __init ima_template_fmt_setup(char *str)
 
 	builtin_templates[num_templates - 1].fmt = str;
 	ima_template = builtin_templates + num_templates - 1;
+	template_setup_done = 1;
 
 	return 1;
 }