platform/x86: think-lmi: Fix reference leak

If a duplicate attribute is found using kset_find_obj(), a reference
to that attribute is returned which needs to be disposed accordingly
using kobject_put(). Move the setting name validation into a separate
function to allow for this change without having to duplicate the
cleanup code for this setting.
As a side note, a very similar bug was fixed in
commit 7295a996fd ("platform/x86: dell-sysman: Fix reference leak"),
so it seems that the bug was copied from that driver.

Compile-tested only.

Fixes: 1bcad8e510 ("platform/x86: think-lmi: Fix issues with duplicate attributes")
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20230925142819.74525-2-W_Armin@gmx.de
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/think-lmi.c

@@ -1248,6 +1248,24 @@ static void tlmi_release_attr(void)
 	kset_unregister(tlmi_priv.authentication_kset);
 }
 
+static int tlmi_validate_setting_name(struct kset *attribute_kset, char *name)
+{
+	struct kobject *duplicate;
+
+	if (!strcmp(name, "Reserved"))
+		return -EINVAL;
+
+	duplicate = kset_find_obj(attribute_kset, name);
+	if (duplicate) {
+		pr_debug("Duplicate attribute name found - %s\n", name);
+		/* kset_find_obj() returns a reference */
+		kobject_put(duplicate);
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
 static int tlmi_sysfs_init(void)
 {
 	int i, ret;
@@ -1276,10 +1294,8 @@ static int tlmi_sysfs_init(void)
 			continue;
 
 		/* check for duplicate or reserved values */
-		if (kset_find_obj(tlmi_priv.attribute_kset, tlmi_priv.setting[i]->display_name) ||
-		    !strcmp(tlmi_priv.setting[i]->display_name, "Reserved")) {
-			pr_debug("duplicate or reserved attribute name found - %s\n",
-				tlmi_priv.setting[i]->display_name);
+		if (tlmi_validate_setting_name(tlmi_priv.attribute_kset,
+					       tlmi_priv.setting[i]->display_name) < 0) {
 			kfree(tlmi_priv.setting[i]->possible_values);
 			kfree(tlmi_priv.setting[i]);
 			tlmi_priv.setting[i] = NULL;