In the Linux kernel, the following vulnerability has been resolved: thermal: hwmon: Remove hwmon class device along with its parent The cu

In the Linux kernel, the following vulnerability has been resolved:

thermal: hwmon: Remove hwmon class device along with its parent

The current code creates one hwmon device per thermal zone type and that
device is registered under the first thermal zone of the given type.

That turns out to be problematic when the thermal zone holding the
hwmon device is removed.

For example, say that there are two ACPI thermal zones on a system

/sys/devices/virtual/thermal/thermal_zone0/
/sys/devices/virtual/thermal/thermal_zone1/

The current code registers a hwmon class device for thermal_zone0 only:

/sys/devices/virtual/thermal/thermal_zone0/hwmon0/

because the type is "acpitz" for both of them, but it adds a sysfs
attribute that belongs to thermal_zone1 under it:

/sys/devices/virtual/thermal/thermal_zone0/hwmon0/temp2_input

There is also

/sys/devices/virtual/thermal/thermal_zone0/hwmon0/temp1_input

which belongs to thermal_zone0.

When thermal_zone0 is removed, say because the ACPI thermal driver is
unbound from the underlying platform device, thermal_remove_hwmon_sysfs()
skips the removal of hwmon0 because of the temp2_input attribute
belonging to thermal_zone1 which effectively prevents thermal_zone0
removal from making progress.

Address this by making thermal_remove_hwmon_sysfs() remove the entire
hwmon class device interface for the given thermal zone type when the
thermal zone device holding it is removed.

To prevent races with thermal_add_hwmon_sysfs() that may interfere
with this, carry out the entire addition and removal of hwmon sysfs
interfaces for thermal zones under thermal_hwmon_list_lock.

Also adjust the layout of the labels in thermal_add_hwmon_sysfs() to
the current kernel coding style to align with the new "unlock" label.