platform/x86: dell-wmi-sysman: Fix possible NULL pointer deref on exit

It is possible for release_attributes_data() to get called when the
main_dir_kset has not been created yet, move the removal of the bios-reset
sysfs attr to under a if (main_dir_kset) check to avoid a NULL pointer
deref.

Fixes: e8a60aa7404b ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Cc: Divya Bharathi <Divya_Bharathi@dell.com>
Cc: Mario Limonciello <mario.limonciello@dell.com>
Reported-by: Alexander Naumann <alexandernaumann@gmx.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210321115901.35072-3-hdegoede@redhat.com

diff --git a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
index c1997db74cca53c8b41e1d09967ef675cfcb0727..8b251b2c37a2d722d01a6fec89f57bf4e334cfeb 100644 (file)
--- a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
+++ b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
@@ -225,12 +225,6 @@ static int create_attributes_level_sysfs_files(void)
        return ret;
 }
 
-static void release_reset_bios_data(void)
-{
-       sysfs_remove_file(&wmi_priv.main_dir_kset->kobj, &reset_bios.attr);
-       sysfs_remove_file(&wmi_priv.main_dir_kset->kobj, &pending_reboot.attr);
-}
-
 static ssize_t wmi_sysman_attr_show(struct kobject *kobj, struct attribute *attr,
                                    char *buf)
 {
@@ -373,8 +367,6 @@ static void destroy_attribute_objs(struct kset *kset)
  */
 static void release_attributes_data(void)
 {
-       release_reset_bios_data();
-
        mutex_lock(&wmi_priv.mutex);
        exit_enum_attributes();
        exit_int_attributes();
@@ -386,12 +378,13 @@ static void release_attributes_data(void)
                wmi_priv.authentication_dir_kset = NULL;
        }
        if (wmi_priv.main_dir_kset) {
+               sysfs_remove_file(&wmi_priv.main_dir_kset->kobj, &reset_bios.attr);
+               sysfs_remove_file(&wmi_priv.main_dir_kset->kobj, &pending_reboot.attr);
                destroy_attribute_objs(wmi_priv.main_dir_kset);
                kset_unregister(wmi_priv.main_dir_kset);
                wmi_priv.main_dir_kset = NULL;
        }
        mutex_unlock(&wmi_priv.mutex);
-
 }
 
 /**