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    Subject[34-longterm 208/247] hwmon: (sht15) Fix integer overflow in humidity calculation
    Date
    From: Vivien Didelot <vivien.didelot@savoirfairelinux.com>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit ccd32e735de7a941906e093f8dca924bb05c5794 upstream.

    An integer overflow occurs in the calculation of RHlinear when the
    relative humidity is greater than around 30%. The consequence is a subtle
    (but noticeable) error in the resulting humidity measurement.

    Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
    Signed-off-by: Jean Delvare <khali@linux-fr.org>
    Cc: Jonathan Cameron <jic23@cam.ac.uk>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    drivers/hwmon/sht15.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c
    index a610e78..38a41d2 100644
    --- a/drivers/hwmon/sht15.c
    +++ b/drivers/hwmon/sht15.c
    @@ -333,11 +333,11 @@ static inline int sht15_calc_humid(struct sht15_data *data)

    const int c1 = -4;
    const int c2 = 40500; /* x 10 ^ -6 */
    - const int c3 = -2800; /* x10 ^ -9 */
    + const int c3 = -28; /* x 10 ^ -7 */

    RHlinear = c1*1000
    + c2 * data->val_humid/1000
    - + (data->val_humid * data->val_humid * c3)/1000000;
    + + (data->val_humid * data->val_humid * c3) / 10000;
    return (temp - 25000) * (10000 + 80 * data->val_humid)
    / 1000000 + RHlinear;
    }
    --
    1.7.4.4


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