linux-kernel - [PATCH 4.17 017/324] hwmon: (nct6775) Fix loop limit

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Message-Id: <20180823074956.770806536@linuxfoundation.org>
Date:   Thu, 23 Aug 2018 09:51:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Paul Menzel <pmenzel+linux-hwmon@...gen.mpg.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.17 017/324] hwmon: (nct6775) Fix loop limit

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

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

From: Guenter Roeck <linux@...ck-us.net>

[ Upstream commit 91bb8f45f73f19a0150c233c0f11cdeb6d71d1e9 ]

Commit cc66b3038254 ("hwmon: (nct6775) Rework temperature source and label
handling") changed a loop limit from "data->temp_label_num - 1" to "32",
as part of moving from a string array to a bit mask. This results in the
following error, reported by UBSAN.

UBSAN: Undefined behaviour in drivers/hwmon/nct6775.c:4179:27
shift exponent 32 is too large for 32-bit type 'long unsigned int'

Similar to the original loop, the limit has to be one less than the
number of bits.

Fixes: cc66b3038254 ("hwmon: (nct6775) Rework temperature source and label handling")
Reported-by: Paul Menzel <pmenzel+linux-hwmon@...gen.mpg.de>
Cc: Paul Menzel <pmenzel+linux-hwmon@...gen.mpg.de>
Tested-by: Paul Menzel <pmenzel+linux-hwmon@...gen.mpg.de>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/hwmon/nct6775.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -4175,7 +4175,7 @@ static int nct6775_probe(struct platform
 	 * The temperature is already monitored if the respective bit in <mask>
 	 * is set.
 	 */
-	for (i = 0; i < 32; i++) {
+	for (i = 0; i < 31; i++) {
 		if (!(data->temp_mask & BIT(i + 1)))
 			continue;
 		if (!reg_temp_alternate[i])