iio: addac: ad74413r: Do not reference negative array offsets
Instead of aiming rx_buf at an invalid array-boundary-crossing location,
just skip the first increment. Seen when building with -Warray-bounds:
drivers/iio/addac/ad74413r.c: In function 'ad74413r_update_scan_mode':
drivers/iio/addac/ad74413r.c:843:22: warning: array subscript -4 is below array bounds of 'u8[16]' { aka 'unsigned char[16]'} [-Warray-bounds]
843 | u8 *rx_buf = &st->adc_samples_buf.rx_buf[-1 * AD74413R_FRAME_SIZE];
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/iio/addac/ad74413r.c:84:20: note: while referencing 'rx_buf'
84 | u8 rx_buf[AD74413R_FRAME_SIZE * AD74413R_CHANNEL_MAX];
| ^~~~~~
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Michael Hennerich <Michael.Hennerich@analog.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: linux-iio@vger.kernel.org
Fixes:
fea251b6a5db ("iio: addac: add AD74413R driver")
Reviewed-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220112203456.3950884-1-keescook@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>