hwmon: (occ) Fix division by zero issue

The code in occ_get_powr_avg() invokes div64_u64() without checking the
divisor. In case the divisor is zero, kernel gets an "Division by zero
in kernel" error.

Check the divisor and make it return 0 if the divisor is 0.

Fixes: c10e753d ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Lei YU <mine260309@gmail.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/1562813088-23708-1-git-send-email-mine260309@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/occ/common.c

@@ -408,8 +408,10 @@ static ssize_t occ_show_power_1(struct device *dev,
 
 static u64 occ_get_powr_avg(u64 *accum, u32 *samples)
 {
-	return div64_u64(get_unaligned_be64(accum) * 1000000ULL,
-			 get_unaligned_be32(samples));
+	u64 divisor = get_unaligned_be32(samples);
+
+	return (divisor == 0) ? 0 :
+		div64_u64(get_unaligned_be64(accum) * 1000000ULL, divisor);
 }
 
 static ssize_t occ_show_power_2(struct device *dev,