platform/x86: dell-wmi-sysman: Make it safe to call exit_foo_attributes() multiple times

During some of the error-exit paths it is possible that
release_attributes_data() will get called multiple times,
which results in exit_foo_attributes() getting called multiple
times.

Make it safe to call exit_foo_attributes() multiple times,
avoiding double-free()s in this case.

Note that release_attributes_data() really should only be called
once during error-exit paths. This will be fixed in a separate patch
and it is good to have the exit_foo_attributes() functions modified
this way regardless.

Fixes: e8a60aa7 ("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>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210321115901.35072-4-hdegoede@redhat.com

drivers/platform/x86/dell/dell-wmi-sysman/enum-attributes.c

@@ -185,5 +185,8 @@ void exit_enum_attributes(void)
 			sysfs_remove_group(wmi_priv.enumeration_data[instance_id].attr_name_kobj,
 								&enumeration_attr_group);
 	}
+	wmi_priv.enumeration_instances_count = 0;
+
 	kfree(wmi_priv.enumeration_data);
+	wmi_priv.enumeration_data = NULL;
 }

drivers/platform/x86/dell/dell-wmi-sysman/int-attributes.c

@@ -175,5 +175,8 @@ void exit_int_attributes(void)
 			sysfs_remove_group(wmi_priv.integer_data[instance_id].attr_name_kobj,
 								&integer_attr_group);
 	}
+	wmi_priv.integer_instances_count = 0;
+
 	kfree(wmi_priv.integer_data);
+	wmi_priv.integer_data = NULL;
 }

drivers/platform/x86/dell/dell-wmi-sysman/passobj-attributes.c

@@ -183,5 +183,8 @@ void exit_po_attributes(void)
 			sysfs_remove_group(wmi_priv.po_data[instance_id].attr_name_kobj,
 								&po_attr_group);
 	}
+	wmi_priv.po_instances_count = 0;
+
 	kfree(wmi_priv.po_data);
+	wmi_priv.po_data = NULL;
 }

drivers/platform/x86/dell/dell-wmi-sysman/string-attributes.c

@@ -155,5 +155,8 @@ void exit_str_attributes(void)
 			sysfs_remove_group(wmi_priv.str_data[instance_id].attr_name_kobj,
 								&str_attr_group);
 	}
+	wmi_priv.str_instances_count = 0;
+
 	kfree(wmi_priv.str_data);
+	wmi_priv.str_data = NULL;
 }