The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 19ef7b70ca9487773c29b449adf0c70f540a0aab Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Nuno=20S=C3=A1?= nuno.sa@analog.com Date: Thu, 12 Nov 2020 15:43:22 +0100 Subject: [PATCH] iio: buffer: Fix demux update MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

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 Sá 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

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index 9663dec3dcf3..2f7426a2f47c 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -853,12 +853,12 @@ static int iio_buffer_update_demux(struct iio_dev *indio_dev, 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); length = iio_storage_bytes_for_si(indio_dev, in_ind); /* 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); } length = iio_storage_bytes_for_si(indio_dev, in_ind); out_loc = roundup(out_loc, length);