FAILED: patch "[PATCH] iio: buffer: Fix demux update" failed to apply to 4.4-stable tree

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 <[email protected]>.

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?= <[email protected]>
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.

index 9663dec3dcf3..2f7426a2f47c 100644
@@ -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);

Hi Greg,

Here is the backport.

--
Regards
Sudip

From 441947967026f382aa78bc51955024995f546543 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nuno=20S=C3=A1?= <[email protected]>
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

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.

---
 drivers/iio/industrialio-buffer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 864a61b05665..d3cdd742972f 100644
@@ -1281,9 +1281,6 @@ 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);
 			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(struct iio_dev *indio_dev,
 				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)

2.11.0

Thanks, now queued up.

greg k-h