From 3d8e3ad879441ae14c5957b933028daf39d252b0 Mon Sep 17 00:00:00 2001
From: Frans Pop <elendil@planet.nl>
Date: Mon, 26 Oct 2009 08:39:02 +0100
Subject: [PATCH] thermal: add sanity check for the passive attribute
Values below 1000 milli-celsius don't make sense and can cause the
system to go into a thermal heart attack: the actual temperature
will always be lower and thus the system will be throttled down to
its lowest setting.
An additional problem is that values below 1000 will show as 0 in
/proc/acpi/thermal/TZx/trip_points:passive.
cat passive
0
echo -n 90 >passive
bash: echo: write error: Invalid argument
echo -n 90000 >passive
cat passive
90000
Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---
Documentation/thermal/sysfs-api.txt | 1 +
drivers/thermal/thermal_sys.c | 6 ++++++
2 files changed, 7 insertions(+)
diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
index a87dc277a5ca49..cb3d15bc1aeb47 100644
--- a/Documentation/thermal/sysfs-api.txt
+++ b/Documentation/thermal/sysfs-api.txt
@@ -206,6 +206,7 @@ passive
passive trip point for the zone. Activation is done by polling with
an interval of 1 second.
Unit: millidegrees Celsius
+ Valid values: 0 (disabled) or greater than 1000
RW, Optional
*****************************
diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
index 6f8d8f971212f3..310e40ab00b6ff 100644
--- a/drivers/thermal/thermal_sys.c
+++ b/drivers/thermal/thermal_sys.c
@@ -225,6 +225,12 @@ passive_store(struct device *dev, struct device_attribute *attr,
if (!sscanf(buf, "%d\n", &state))
return -EINVAL;
+ /* sanity check: values below 1000 millicelcius don't make sense
+ * and can cause the system to go into a thermal heart attack
+ */
+ if (state && state < 1000)
+ return -EINVAL;
+
if (state && !tz->forced_passive) {
mutex_lock(&thermal_list_lock);
list_for_each_entry(cdev, &thermal_cdev_list, node) {
--
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