ima: Fix a potential NULL pointer access in ima_restore_measurement_list

In restore_template_fmt, when kstrdup fails, a non-NULL value will still be
returned, which causes a NULL pointer access in template_desc_init_fields.

Fixes: c7d09367 ("ima: support restoring multiple template formats")
Cc: stable@kernel.org
Co-developed-by: Jiaming Li <lijiaming30@huawei.com>
Signed-off-by: Jiaming Li <lijiaming30@huawei.com>
Signed-off-by: Huaxin Lu <luhuaxin1@huawei.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

security/integrity/ima/ima_template.c

@@ -340,8 +340,11 @@ static struct ima_template_desc *restore_template_fmt(char *template_name)
 
 	template_desc->name = "";
 	template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
-	if (!template_desc->fmt)
+	if (!template_desc->fmt) {
+		kfree(template_desc);
+		template_desc = NULL;
 		goto out;
+	}
 
 	spin_lock(&template_list);
 	list_add_tail_rcu(&template_desc->list, &defined_templates);