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    Subject[PATCH 4.4 070/101] hwmon: (nct7802) Fix overflows seen when writing into limit attributes
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

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

    commit c0d04e9112ad59d73f23f3b0f6726c5e798dfcbf upstream.

    Fix overflows seen when writing voltage and temperature limit attributes.

    The value passed to DIV_ROUND_CLOSEST() needs to be clamped, and the
    value parameter passed to nct7802_write_fan_min() is an unsigned long.

    Also, writing values larger than 2700000 into a fan limit attribute results
    in writing 0 into the chip's limit registers. The exact behavior when
    writing this value is unspecified. For consistency, report a limit of
    1350000 if the chip register reads 0. This may be wrong, and the chip
    behavior should be verified with the actual chip, but it is better than
    reporting a value of 0 (which, when written, results in writing a value
    of 0x1fff into the chip register).

    Fixes: 3434f3783580 ("hwmon: Driver for Nuvoton NCT7802Y")
    Reviewed-by: Jean Delvare <jdelvare@suse.de>
    Signed-off-by: Guenter Roeck <linux@roeck-us.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/hwmon/nct7802.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- a/drivers/hwmon/nct7802.c
    +++ b/drivers/hwmon/nct7802.c
    @@ -259,13 +259,15 @@ static int nct7802_read_fan_min(struct n
    ret = 0;
    else if (ret)
    ret = DIV_ROUND_CLOSEST(1350000U, ret);
    + else
    + ret = 1350000U;
    abort:
    mutex_unlock(&data->access_lock);
    return ret;
    }

    static int nct7802_write_fan_min(struct nct7802_data *data, u8 reg_fan_low,
    - u8 reg_fan_high, unsigned int limit)
    + u8 reg_fan_high, unsigned long limit)
    {
    int err;

    @@ -326,8 +328,8 @@ static int nct7802_write_voltage(struct
    int shift = 8 - REG_VOLTAGE_LIMIT_MSB_SHIFT[index - 1][nr];
    int err;

    + voltage = clamp_val(voltage, 0, 0x3ff * nct7802_vmul[nr]);
    voltage = DIV_ROUND_CLOSEST(voltage, nct7802_vmul[nr]);
    - voltage = clamp_val(voltage, 0, 0x3ff);

    mutex_lock(&data->access_lock);
    err = regmap_write(data->regmap,
    @@ -402,7 +404,7 @@ static ssize_t store_temp(struct device
    if (err < 0)
    return err;

    - val = clamp_val(DIV_ROUND_CLOSEST(val, 1000), -128, 127);
    + val = DIV_ROUND_CLOSEST(clamp_val(val, -128000, 127000), 1000);

    err = regmap_write(data->regmap, nr, val & 0xff);
    return err ? : count;

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