linux-kernel - RE: [PATCH 3.2 140/185] hwmon: Prevent some divide by zeros in FAN_TO

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Message-ID: <C83890AC7B9B4C02AB263C79698F8F96@honeybadger>
Date:	Mon, 30 Dec 2013 09:15:09 -0000
From:	<vt8231@...denengine.co.uk>
To:	"'Ben Hutchings'" <ben@...adent.org.uk>
Cc:	<akpm@...ux-foundation.org>,
	"'Roger Lucas'" <vt8231@...denengine.co.uk>,
	"'Dan Carpenter'" <dan.carpenter@...cle.com>,
	"'Jean Delvare'" <khali@...ux-fr.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: RE: [PATCH 3.2 140/185] hwmon: Prevent some divide by zeros in FAN_TO_REG()

Hi Ben,

The VT8231 patch looks OK to me.  Thanks for your help.

Best regards,

Roger

-----Original Message-----
From: Ben Hutchings [mailto:ben@...adent.org.uk] 
Sent: 29 December 2013 02:09
To: linux-kernel@...r.kernel.org; stable@...r.kernel.org
Cc: akpm@...ux-foundation.org; Roger Lucas; Dan Carpenter; Jean Delvare
Subject: [PATCH 3.2 140/185] hwmon: Prevent some divide by zeros in
FAN_TO_REG()

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Dan Carpenter <dan.carpenter@...cle.com>

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@...cle.com>
Acked-by: Roger Lucas <vt8231@...denengine.co.uk>
Signed-off-by: Jean Delvare <khali@...ux-fr.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/hwmon/lm78.c    | 2 ++
 drivers/hwmon/sis5595.c | 2 ++
 drivers/hwmon/vt8231.c  | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/hwmon/lm78.c
+++ b/drivers/hwmon/lm78.c
@@ -90,6 +90,8 @@ static inline u8 FAN_TO_REG(long rpm, in
 {
 	if (rpm <= 0)
 		return 255;
+	if (rpm > 1350000)
+		return 1;
 	return SENSORS_LIMIT((1350000 + rpm * div / 2) / (rpm * div), 1,
254);
 }
 
--- a/drivers/hwmon/sis5595.c
+++ b/drivers/hwmon/sis5595.c
@@ -133,6 +133,8 @@ static inline u8 FAN_TO_REG(long rpm, in
 {
 	if (rpm <= 0)
 		return 255;
+	if (rpm > 1350000)
+		return 1;
 	return SENSORS_LIMIT((1350000 + rpm * div / 2) / (rpm * div), 1,
254);
 }
 
--- a/drivers/hwmon/vt8231.c
+++ b/drivers/hwmon/vt8231.c
@@ -139,7 +139,7 @@ static const u8 regtempmin[] = { 0x3a, 0
 */
 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);
 }


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