From: "Nuno S�" nuno.sa@analog.com
commit 19ef7b70ca9487773c29b449adf0c70f540a0aab upstream
When updating the buffer demux, we will skip a scan element from the device in the case `in_ind != out_ind` and we enter the while loop. in_ind should only be refreshed with `find_next_bit()` in the end of the loop.
Note, to cause problems we need a situation where we are skippig over an element (channel not enabled) that happens to not have the same size as the next element. Whilst this is a possible situation we haven't actually identified any cases in mainline where it happens as most drivers have consistent channel storage sizes with the exception of the timestamp which is the last element and hence never skipped over.
Fixes: 5ada4ea9be16 ("staging:iio: add demux optionally to path from device to buffer") Signed-off-by: Nuno S� nuno.sa@analog.com Link: https://lore.kernel.org/r/20201112144323.28887-1-nuno.sa@analog.com Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com [sudip: adjust context] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iio/industrialio-buffer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -1281,9 +1281,6 @@ static int iio_buffer_update_demux(struc indio_dev->masklength, in_ind + 1); while (in_ind != out_ind) { - in_ind = find_next_bit(indio_dev->active_scan_mask, - indio_dev->masklength, - in_ind + 1); ch = iio_find_channel_from_si(indio_dev, in_ind); if (ch->scan_type.repeat > 1) length = ch->scan_type.storagebits / 8 * @@ -1292,6 +1289,9 @@ static int iio_buffer_update_demux(struc length = ch->scan_type.storagebits / 8; /* Make sure we are aligned */ in_loc = roundup(in_loc, length) + length; + in_ind = find_next_bit(indio_dev->active_scan_mask, + indio_dev->masklength, + in_ind + 1); } ch = iio_find_channel_from_si(indio_dev, in_ind); if (ch->scan_type.repeat > 1)