[PATCH] thermal: sysfs: Perform bounds check when storing thermal states

[Varad Gautam <varadgautam@google.com>]

Check that a user-provided thermal state is within the maximum
thermal states supported by a given driver before attempting to
apply it. This prevents a subsequent OOB access in
thermal_cooling_device_stats_update() while performing
state-transition accounting on drivers that do not have this check
in their set_cur_state() handle.

Signed-off-by: Varad Gautam <varadgautam@google.com>
Cc: stable@vger.kernel.org
---
 drivers/thermal/thermal_sysfs.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 1c4aac8464a7..0c6b0223b133 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -607,7 +607,7 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t count)
 {
 	struct thermal_cooling_device *cdev = to_cooling_device(dev);
-	unsigned long state;
+	unsigned long state, max_state;
 	int result;
 
 	if (sscanf(buf, "%ld\n", &state) != 1)
@@ -618,10 +618,20 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
 
 	mutex_lock(&cdev->lock);
 
+	result = cdev->ops->get_max_state(cdev, &max_state);
+	if (result)
+		goto unlock;
+
+	if (state > max_state) {
+		result = -EINVAL;
+		goto unlock;
+	}
+
 	result = cdev->ops->set_cur_state(cdev, state);
 	if (!result)
 		thermal_cooling_device_stats_update(cdev, state);
 
+unlock:
 	mutex_unlock(&cdev->lock);
 	return result ? result : count;
 }
-- 
2.37.0.rc0.161.g10f37bed90-goog