[PATCH 3.5 094/103] hwmon: Prevent some divide by zeros in FAN_TO_REG()

[Luis Henriques]

3.5.7.28 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 3806b45ba4655147a011df03242cc197ab986c43 upstream.

The "rpm * div" operations can overflow here, so this patch adds an
upper limit to rpm to prevent that.  Jean Delvare helped me with this
patch.

Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Acked-by: Roger Lucas <vt8231@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/hwmon/lm78.c    | 2 ++
 drivers/hwmon/sis5595.c | 2 ++
 drivers/hwmon/vt8231.c  | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/lm78.c b/drivers/hwmon/lm78.c
index f6bc414..8d6a133 100644
--- a/drivers/hwmon/lm78.c
+++ b/drivers/hwmon/lm78.c
@@ -94,6 +94,8 @@ static inline u8 FAN_TO_REG(long rpm, int div)
 {
 	if (rpm <= 0)
 		return 255;
+	if (rpm > 1350000)
+		return 1;
 	return SENSORS_LIMIT((1350000 + rpm * div / 2) / (rpm * div), 1, 254);
 }
 
diff --git a/drivers/hwmon/sis5595.c b/drivers/hwmon/sis5595.c
index 6c4d8eb..098489c 100644
--- a/drivers/hwmon/sis5595.c
+++ b/drivers/hwmon/sis5595.c
@@ -141,6 +141,8 @@ static inline u8 FAN_TO_REG(long rpm, int div)
 {
 	if (rpm <= 0)
 		return 255;
+	if (rpm > 1350000)
+		return 1;
 	return SENSORS_LIMIT((1350000 + rpm * div / 2) / (rpm * div), 1, 254);
 }
 
diff --git a/drivers/hwmon/vt8231.c b/drivers/hwmon/vt8231.c
index 386a845..0a287e0 100644
--- a/drivers/hwmon/vt8231.c
+++ b/drivers/hwmon/vt8231.c
@@ -145,7 +145,7 @@ static const u8 regtempmin[] = { 0x3a, 0x3e, 0x2c, 0x2e, 0x30, 0x32 };
  */
 static inline u8 FAN_TO_REG(long rpm, int div)
 {
-	if (rpm == 0)
+	if (rpm <= 0 || rpm > 1310720)
 		return 0;
 	return SENSORS_LIMIT(1310720 / (rpm * div), 1, 255);
 }
-- 
1.8.3.2

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