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From:   Lei YU <mine260309@gmail.com>
To:     Jean Delvare <jdelvare@suse.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Eddie James <eajames@linux.ibm.com>,
        "Gustavo A . R . Silva" <gustavo@embeddedor.com>,
        Lei YU <mine260309@gmail.com>, linux-hwmon@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] hwmon (occ): Fix division by zero issue
Date:   Thu, 11 Jul 2019 10:44:48 +0800
Message-Id: <1562813088-23708-1-git-send-email-mine260309@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

Signed-off-by: Lei YU <mine260309@gmail.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/hwmon/occ/common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 13a6290..f02aa40 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -402,8 +402,10 @@ 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,
-- 
2.7.4