thermal: intel: x86_pkg_temp_thermal: Add lower bound check for sysfs input

When setting a trip point temperature from sysfs, there is an upper
bound check on the user input, but no lower bound check.

As hardware register has 7 bits for a trip point temperature, the offset
to tj_max of the input temperature must be equal to/less than 0x7f.
Or else,
 1. bogus temperature is updated into the trip temperature bits.
 2. the upper bits of the register can be polluted.

For example,
$ rdmsr 0x1b2
2000003
$ echo -180000 > /sys/class/thermal/thermal_zone1/trip_point_1_temp
$ rdmsr 0x1b2
3980003

Not only the trip point temp is set to 76C on this platform (tj_max is
100), the Power Notification (Bit 24) is also enabled erronously.

Fix the problem by adding lower bound check for sysfs input.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/all/add7a378-4d50-4ba1-81d3-a0c17db25a0b@kili.mountain/
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/thermal/intel/x86_pkg_temp_thermal.c b/drivers/thermal/intel/x86_pkg_temp_thermal.c
index 1c2de84..128ee02 100644 (file)
--- a/drivers/thermal/intel/x86_pkg_temp_thermal.c
+++ b/drivers/thermal/intel/x86_pkg_temp_thermal.c
@@ -124,14 +124,16 @@ sys_set_trip_temp(struct thermal_zone_device *tzd, int trip, int temp)
 {
        struct zone_device *zonedev = tzd->devdata;
        u32 l, h, mask, shift, intr;
-       int tj_max, ret;
+       int tj_max, val, ret;
 
        tj_max = intel_tcc_get_tjmax(zonedev->cpu);
        if (tj_max < 0)
                return tj_max;
        tj_max *= 1000;
 
-       if (trip >= MAX_NUMBER_OF_TRIPS || temp >= tj_max)
+       val = (tj_max - temp)/1000;
+
+       if (trip >= MAX_NUMBER_OF_TRIPS || val < 0 || val > 0x7f)
                return -EINVAL;
 
        ret = rdmsr_on_cpu(zonedev->cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT,
@@ -156,7 +158,7 @@ sys_set_trip_temp(struct thermal_zone_device *tzd, int trip, int temp)
        if (!temp) {
                l &= ~intr;
        } else {
-               l |= (tj_max - temp)/1000 << shift;
+               l |= val << shift;
                l |= intr;
        }