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[17/25] iio:adc:ti-adc084s021 Fix alignment and data leak issues.

Message ID 20200525170628.503283-18-jic23@kernel.org (mailing list archive)
State New, archived
Headers show
Series IIO: 2nd set of timestamp alignment fixes. | expand

Commit Message

Jonathan Cameron May 25, 2020, 5:06 p.m. UTC
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

One of a class of bugs pointed out by Lars in a recent review.
iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
to the size of the timestamp (8 bytes).  This is not guaranteed in
this driver which uses an array of smaller elements on the stack.
As Lars also noted this anti pattern can involve a leak of data to
userspace and that indeed can happen here.  We close both issues by
moving to a suitable structure in the iio_priv().

This data is allocated with kzalloc so no data can leak apart from
previous readings.

Fixes: 3691e5a69449 ("iio: adc: add driver for the ti-adc084s021 chip")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: MÃ¥rten Lindahl <martenli@axis.com>
---
 drivers/iio/adc/ti-adc084s021.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)
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Patch

diff --git a/drivers/iio/adc/ti-adc084s021.c b/drivers/iio/adc/ti-adc084s021.c
index bdedf456ee05..36d874cced9d 100644
--- a/drivers/iio/adc/ti-adc084s021.c
+++ b/drivers/iio/adc/ti-adc084s021.c
@@ -25,6 +25,11 @@  struct adc084s021 {
 	struct spi_transfer spi_trans;
 	struct regulator *reg;
 	struct mutex lock;
+	/* Buffer used to align data */
+	struct {
+		__be16 channels[4];
+		s64 ts;
+	} scan;
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache line.
@@ -140,14 +145,13 @@  static irqreturn_t adc084s021_buffer_trigger_handler(int irq, void *pollfunc)
 	struct iio_poll_func *pf = pollfunc;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct adc084s021 *adc = iio_priv(indio_dev);
-	__be16 data[8] = {0}; /* 4 * 16-bit words of data + 8 bytes timestamp */
 
 	mutex_lock(&adc->lock);
 
-	if (adc084s021_adc_conversion(adc, &data) < 0)
+	if (adc084s021_adc_conversion(adc, adc->scan.channels) < 0)
 		dev_err(&adc->spi->dev, "Failed to read data\n");
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &adc->scan,
 					   iio_get_time_ns(indio_dev));
 	mutex_unlock(&adc->lock);
 	iio_trigger_notify_done(indio_dev->trig);