hwmon: Prevent some divide by zeros in FAN_TO_REG()

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@oracle.com>
Acked-by: Roger Lucas <vt8231@hiddenengine.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Jean Delvare <khali@linux-fr.org>

3 files changed, 5 insertions, 1 deletions

diff --git a/drivers/hwmon/lm78.c b/drivers/hwmon/lm78.c
index 6cf6bff79003..a2f3b4a365e4 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 clamp_val((1350000 + rpm * div / 2) / (rpm * div), 1, 254);
 }
 
diff --git a/drivers/hwmon/sis5595.c b/drivers/hwmon/sis5595.c
index 1404e6319deb..72a889702f0d 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 clamp_val((1350000 + rpm * div / 2) / (rpm * div), 1, 254);
 }
 
diff --git a/drivers/hwmon/vt8231.c b/drivers/hwmon/vt8231.c
index 0e7017841f7d..aee14e2192f8 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 clamp_val(1310720 / (rpm * div), 1, 255);
 }