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Message-ID: <1eb0428d352be2498739de71eb65746309c90f4c.camel@perches.com>
Subject: Re: [PATCH] iio: tsl2583: Fix division by a zero lux_val
From:   Joe Perches <joe@perches.com>
To:     Jonathan Cameron <jic23@kernel.org>,
        Colin King <colin.king@canonical.com>
Cc:     Lars-Peter Clausen <lars@metafoo.de>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Jon Brenner <jbrenner@taosinc.com>, linux-iio@vger.kernel.org,
        clang-built-linux@googlegroups.com,
        kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Sat, 08 May 2021 10:01:14 -0700
In-Reply-To: <20210508171258.2ef71a70@jic23-huawei>
References: <20210507183041.115864-1-colin.king@canonical.com>
         <20210508171258.2ef71a70@jic23-huawei>
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On Sat, 2021-05-08 at 17:12 +0100, Jonathan Cameron wrote:
> On Fri,  7 May 2021 19:30:41 +0100 Colin King <colin.king@canonical.com> wrote:
[]
> > The lux_val returned from tsl2583_get_lux can potentially be zero,
> > so check for this to avoid a division by zero and an overflowed
> > gain_trim_val.
[]
> > Fixes: ac4f6eee8fe8 ("staging: iio: TAOS tsl258x: Device driver")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> Definitely looks like it could happen so applied to the fixes-togreg branch of
> iio.git and marked for stable.
[]
> > diff --git a/drivers/iio/light/tsl2583.c b/drivers/iio/light/tsl2583.c
[]
> > @@ -341,6 +341,14 @@ static int tsl2583_als_calibrate(struct iio_dev *indio_dev)
> > ?		return lux_val;
> > ?	}
> > 
> > +	/* Avoid division by zero of lux_value later on */
> > +	if (lux_val == 0) {
> > +		dev_err(&chip->client->dev,
> > +			"%s: lux_val of 0 will produce out of range trim_value\n",
> > +			__func__);
> > +		return -ENODATA;
> > +	}
> > +
> > ?	gain_trim_val = (unsigned int)(((chip->als_settings.als_cal_target)
> > ?			* chip->als_settings.als_gain_trim) / lux_val);

Is a multiplication overflow possible here?
There are also unnecessary parentheses.