On 12/13/2016 01:56 AM, Jean Delvare wrote:
On Sun, 4 Dec 2016 20:55:40 -0800, Guenter Roeck wrote:
Writes into limit attributes can overflow due to multplications
and additions with unbound input values.
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/hwmon/gl520sm.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/hwmon/gl520sm.c b/drivers/hwmon/gl520sm.c
index dee93ec87d02..4bb37d7234b1 100644
--- a/drivers/hwmon/gl520sm.c
+++ b/drivers/hwmon/gl520sm.c
@@ -209,10 +209,11 @@ static ssize_t get_cpu_vid(struct device *dev, struct device_attribute *attr,
static DEVICE_ATTR(cpu0_vid, S_IRUGO, get_cpu_vid, NULL);
#define VDD_FROM_REG(val) (((val) * 95 + 2) / 4)
-#define VDD_TO_REG(val) clamp_val((((val) * 4 + 47) / 95), 0, 255)
+#define VDD_TO_REG(val) \
+ DIV_ROUND_CLOSEST(clamp_val(val, 0, 255 * 95 / 4) * 4, 95)
#define IN_FROM_REG(val) ((val) * 19)
-#define IN_TO_REG(val) clamp_val((((val) + 9) / 19), 0, 255)
+#define IN_TO_REG(val) DIV_ROUND_CLOSEST(clamp_val(val, 0, 255 * 19), 19)
static ssize_t get_in_input(struct device *dev, struct device_attribute *attr,
char *buf)
@@ -514,8 +515,8 @@ static DEVICE_ATTR(fan1_off, S_IRUGO | S_IWUSR,
get_fan_off, set_fan_off);
#define TEMP_FROM_REG(val) (((val) - 130) * 1000)
-#define TEMP_TO_REG(val) clamp_val(((((val) < 0 ? \
- (val) - 500 : (val) + 500) / 1000) + 130), 0, 255)
+#define TEMP_TO_REG(val) (DIV_ROUND_CLOSEST(clamp_val(val, -130000, 125000), \
+ 1000) + 130)
static ssize_t get_temp_input(struct device *dev, struct device_attribute *attr,
char *buf)
Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
But I think FAN_TO_REG can overflow too? Input value is left-shifted
without a prior check.
You are right. My older script didn't detect that because the overflow happens
with a very low value, and the script just concluded that the value range was [0,0].
After improving my test script, the driver generates KASAN bad memory reports.
Outch. I'll have to look into that.
Thanks,
Guenter
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