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    SubjectRe: [patch] iio: tsl2583: make array large enough
    On Thu, Nov 24, 2016 at 05:54:17PM +0100, walter harms wrote:
    >
    >
    > Am 24.11.2016 16:48, schrieb Brian Masney:
    > > On Thu, Nov 24, 2016 at 04:38:07PM +0300, Dan Carpenter wrote:
    > >> This array is supposed to have 10 elements. Smatch complains that with
    > >> the current code we can have n == max_ints and read beyond the end of
    > >> the array.
    > >>
    > >> Fixes: ac4f6eee8fe8 ("staging: iio: TAOS tsl258x: Device driver")
    > >> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    > >>
    > >> diff --git a/drivers/iio/light/tsl2583.c b/drivers/iio/light/tsl2583.c
    > >> index 0b87f6a..a78b602 100644
    > >> --- a/drivers/iio/light/tsl2583.c
    > >> +++ b/drivers/iio/light/tsl2583.c
    > >> @@ -565,7 +565,7 @@ static ssize_t in_illuminance_lux_table_store(struct device *dev,
    > >> struct iio_dev *indio_dev = dev_to_iio_dev(dev);
    > >> struct tsl2583_chip *chip = iio_priv(indio_dev);
    > >> const unsigned int max_ints = TSL2583_MAX_LUX_TABLE_ENTRIES * 3;
    > >> - int value[TSL2583_MAX_LUX_TABLE_ENTRIES * 3];
    > >> + int value[TSL2583_MAX_LUX_TABLE_ENTRIES * 3 + 1];
    > >> int ret = -EINVAL;
    > >> unsigned int n;
    > >>
    > >
    >
    > sorry i did not notice that bevor ..
    > there is a
    > max_ints = TSL2583_MAX_LUX_TABLE_ENTRIES * 3
    >
    > IMHO this should read either:
    > int value[max_ints+1];

    I originally went this route when I refactored the function, however
    running make C=1 yields the following warnings:

    drivers/iio/light/tsl2583.c:568:19: warning: Variable length array is
    used.
    drivers/iio/light/tsl2583.c:574:26: error: cannot size expression

    That is why I went with the current implementation.

    > or
    > max_ints=ARRAY_SIZE(value)-1;
    >
    > (my personal favorite is dropping max_ints completely).

    The max_ints value is also shown in the error message if the user passes
    in too many or too few entries in the per device lux table. I wanted the
    user to see the maximum allowable number without having to dig through
    the kernel source code. Without it, I would have had to duplicate the
    TSL2583_MAX_LUX_TABLE_ENTRIES * 3 statement a third time.

    Brian

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