linux-kernel - [PATCH v4] iio: light: as73211: fix channel handling in only-color triggered buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20241214-iio_memset_scan_holes-v4-1-260b395b8ed5@gmail.com>
Date: Sat, 14 Dec 2024 23:55:50 +0100
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, Christian Eggers <ceggers@...i.de>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: [PATCH v4] iio: light: as73211: fix channel handling in only-color
 triggered buffer

The channel index is off by one unit if AS73211_SCAN_MASK_ALL is not
set (optimized path for color channel readings), and it must be shifted
instead of leaving an empty channel for the temperature when it is off.

Once the channel index is fixed, the uninitialized channel must be set
to zero to avoid pushing uninitialized data.

Add available_scan_masks for all channels and only-color channels to let
the IIO core demux and repack the enabled channels.

Cc: stable@...r.kernel.org
Fixes: 403e5586b52e ("iio: light: as73211: New driver")
Tested-by: Christian Eggers <ceggers@...i.de>
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
---
This issue was found after attempting to make the same mistake for
a driver I maintain, which was fortunately spotted by Jonathan [1].

Keeping old sensor values if the channel configuration changes is known
and not considered an issue, which is also mentioned in [1], so it has
not been addressed by this series. That keeps most of the drivers out
of the way because they store the scan element in iio private data,
which is kzalloc() allocated.

This series only addresses cases where uninitialized i.e. unknown data
is pushed to the userspace, either due to holes in structs or
uninitialized struct members/array elements.

While analyzing involved functions, I found and fixed some triviality
(wrong function name) in the documentation of iio_dev_opaque.

Link: https://lore.kernel.org/linux-iio/20241123151634.303aa860@jic23-huawei/ [1]
---
Changes in v4:
- Fix as73211_scan_masks[] (first MASK_COLOR, then MASK_ALL, no comma
  after 0 i.e. the last element).
- Link to v3: https://lore.kernel.org/r/20241212-iio_memset_scan_holes-v3-1-7f496b6f7222@gmail.com

Changes in v3:
- as73211.c: add available_scan_masks for all channels and only-color
  channels to let the IIO core demux and repack the enabled channels.
- Link to v2: https://lore.kernel.org/r/20241204-iio_memset_scan_holes-v2-0-3f941592a76d@gmail.com

Changes in v2:
- as73211.c: shift channels if no temperature is available and
  initialize chan[3] to zero.
- Link to v1: https://lore.kernel.org/r/20241125-iio_memset_scan_holes-v1-0-0cb6e98d895c@gmail.com
---
 drivers/iio/light/as73211.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/light/as73211.c b/drivers/iio/light/as73211.c
index be0068081ebb..11fbdcdd26d6 100644
--- a/drivers/iio/light/as73211.c
+++ b/drivers/iio/light/as73211.c
@@ -177,6 +177,12 @@ struct as73211_data {
 	BIT(AS73211_SCAN_INDEX_TEMP) | \
 	AS73211_SCAN_MASK_COLOR)
 
+static const unsigned long as73211_scan_masks[] = {
+	AS73211_SCAN_MASK_COLOR,
+	AS73211_SCAN_MASK_ALL,
+	0
+};
+
 static const struct iio_chan_spec as73211_channels[] = {
 	{
 		.type = IIO_TEMP,
@@ -672,9 +678,12 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
 
 		/* AS73211 starts reading at address 2 */
 		ret = i2c_master_recv(data->client,
-				(char *)&scan.chan[1], 3 * sizeof(scan.chan[1]));
+				(char *)&scan.chan[0], 3 * sizeof(scan.chan[0]));
 		if (ret < 0)
 			goto done;
+
+		/* Avoid pushing uninitialized data */
+		scan.chan[3] = 0;
 	}
 
 	if (data_result) {
@@ -682,9 +691,15 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
 		 * Saturate all channels (in case of overflows). Temperature channel
 		 * is not affected by overflows.
 		 */
-		scan.chan[1] = cpu_to_le16(U16_MAX);
-		scan.chan[2] = cpu_to_le16(U16_MAX);
-		scan.chan[3] = cpu_to_le16(U16_MAX);
+		if (*indio_dev->active_scan_mask == AS73211_SCAN_MASK_ALL) {
+			scan.chan[1] = cpu_to_le16(U16_MAX);
+			scan.chan[2] = cpu_to_le16(U16_MAX);
+			scan.chan[3] = cpu_to_le16(U16_MAX);
+		} else {
+			scan.chan[0] = cpu_to_le16(U16_MAX);
+			scan.chan[1] = cpu_to_le16(U16_MAX);
+			scan.chan[2] = cpu_to_le16(U16_MAX);
+		}
 	}
 
 	iio_push_to_buffers_with_timestamp(indio_dev, &scan, iio_get_time_ns(indio_dev));
@@ -758,6 +773,7 @@ static int as73211_probe(struct i2c_client *client)
 	indio_dev->channels = data->spec_dev->channels;
 	indio_dev->num_channels = data->spec_dev->num_channels;
 	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->available_scan_masks = as73211_scan_masks;
 
 	ret = i2c_smbus_read_byte_data(data->client, AS73211_REG_OSR);
 	if (ret < 0)

---
base-commit: 91e71d606356e50f238d7a87aacdee4abc427f07
change-id: 20241123-iio_memset_scan_holes-a673833ef932

Best regards,
-- 
Javier Carrasco <javier.carrasco.cruz@...il.com>