linux-kernel - [PATCH 5.4 33/65] thermal/drivers/rcar_gen3: Fix undefined temperature if negative

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Date:   Tue,  7 Jul 2020 17:17:12 +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, Van Do <van.do.xw@...esas.com>,
        Dien Pham <dien.pham.ry@...esas.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Niklas Soderlund <niklas.soderlund+renesas@...natech.se>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 33/65] thermal/drivers/rcar_gen3: Fix undefined temperature if negative

From: Dien Pham <dien.pham.ry@...esas.com>

[ Upstream commit 5f8f06425a0dcdad7bedbb77e67f5c65ab4dacfc ]

As description for DIV_ROUND_CLOSEST in file include/linux/kernel.h.
  "Result is undefined for negative divisors if the dividend variable
   type is unsigned and for negative dividends if the divisor variable
   type is unsigned."

In current code, the FIXPT_DIV uses DIV_ROUND_CLOSEST but has not
checked sign of divisor before using. It makes undefined temperature
value in case the value is negative.

This patch fixes to satisfy DIV_ROUND_CLOSEST description
and fix bug too. Note that the variable name "reg" is not good
because it should be the same type as rcar_gen3_thermal_read().
However, it's better to rename the "reg" in a further patch as
cleanup.

Signed-off-by: Van Do <van.do.xw@...esas.com>
Signed-off-by: Dien Pham <dien.pham.ry@...esas.com>
[shimoda: minor fixes, add Fixes tag]
Fixes: 564e73d283af ("thermal: rcar_gen3_thermal: Add R-Car Gen3 thermal driver")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Reviewed-by: Niklas Soderlund <niklas.soderlund+renesas@...natech.se>
Tested-by: Niklas Soderlund <niklas.soderlund+renesas@...natech.se>
Reviewed-by: Amit Kucheria <amit.kucheria@...aro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
Link: https://lore.kernel.org/r/1593085099-2057-1-git-send-email-yoshihiro.shimoda.uh@renesas.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/thermal/rcar_gen3_thermal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
index 755d2b5bd2c2b..1ab2ffff4e7c7 100644
--- a/drivers/thermal/rcar_gen3_thermal.c
+++ b/drivers/thermal/rcar_gen3_thermal.c
@@ -169,7 +169,7 @@ static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
 {
 	struct rcar_gen3_thermal_tsc *tsc = devdata;
 	int mcelsius, val;
-	u32 reg;
+	int reg;
 
 	/* Read register and convert to mili Celsius */
 	reg = rcar_gen3_thermal_read(tsc, REG_GEN3_TEMP) & CTEMP_MASK;
-- 
2.25.1