thermal_sys: check get_temp return value

The return value of the get_temp function is not checked when doing a
thermal zone update.  This may lead to a critical shutdown if get_temp
fails and the content of the temp variable is incorrectly set higher than
the critical trip point.

This has been observed on a system with incorrect ACPI implementation
where the corresponding methods were not serialized and therefore
sometimes triggered ACPI errors (AE_ALREADY_EXISTS).  The following
critical shutdowns indicated a temperature of 2097 C, which was obviously
wrong.

The patch adds a return value check that jumps over all trip point
evaluations printing a warning if get_temp fails.  The trip points are
evaluated again on the next polling interval with successful get_temp
execution.

Signed-off-by: Michael Brunner <mibru@gmx.de>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
index 0a69672097a..4e83c297ec9 100644
--- a/drivers/thermal/thermal_sys.c
+++ b/drivers/thermal/thermal_sys.c
@@ -953,7 +953,12 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
 
         mutex_lock(&tz->lock);
 
-        tz->ops->get_temp(tz, &temp);
+        if (tz->ops->get_temp(tz, &temp)) {
+                /* get_temp failed - retry it later */
+                printk(KERN_WARNING PREFIX "failed to read out thermal zone "
+                       "%d\n", tz->id);
+                goto leave;
+        }
 
         for (count = 0; count < tz->trips; count++) {
                 tz->ops->get_trip_type(tz, count, &trip_type);
@@ -1005,6 +1010,8 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
                                             THERMAL_TRIPS_NONE);
 
         tz->last_temperature = temp;
+
+      leave:
         if (tz->passive)
                 thermal_zone_device_set_polling(tz, tz->passive_delay);
         else if (tz->polling_delay)