linux-kernel - Re: ADT746X: logical-bitwise & confusion in set_max_duty_at

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Message-Id: <64d5b5e6dfd0d1820d21db323ef88e25@kernel.crashing.org>
Date:	Mon, 10 Mar 2008 10:13:34 +0100
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	Roel Kluin <12o3l@...cali.nl>
Cc:	benh@...nel.crashing.org, linuxppc-dev@...abs.org,
	lkml <linux-kernel@...r.kernel.org>,
	Colin Leroy <colin@...ino.net>
Subject: Re: ADT746X: logical-bitwise & confusion in set_max_duty_at_crit()

> diff --git a/drivers/hwmon/adt7473.c b/drivers/hwmon/adt7473.c
> index 9587869..8ea7da2 100644
> --- a/drivers/hwmon/adt7473.c
> +++ b/drivers/hwmon/adt7473.c
> @@ -570,7 +570,7 @@ static ssize_t set_max_duty_at_crit(struct device 
> *dev,
>  	struct i2c_client *client = to_i2c_client(dev);
>  	struct adt7473_data *data = i2c_get_clientdata(client);
>  	int temp = simple_strtol(buf, NULL, 10);
> -	temp = temp && 0xFF;
> +	temp &= 0xFF;
>
>  	mutex_lock(&data->lock);
>  	data->max_duty_at_overheat = temp;

The & 0xff here is bogus anyway; temp is only ever used as an u8,
so just declare it as that, or do proper overflow/underflow checking
on it.  The patch will need testing on hardware too, since it changes
behaviour (it should be a bugfix, but who knows).


Segher

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