[v3,24/27] iio:adc:ti-adc0832 Fix alignment issue with timestamp
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Message ID 20200722155103.979802-25-jic23@kernel.org
State New
Headers show
  • IIO: Fused set 1 and 2 of timestamp alignment fixes
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Commit Message

Jonathan Cameron July 22, 2020, 3:51 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.

We fix this issues by moving to a suitable structure in the iio_priv()
data with alignment explicitly requested.  This data is allocated
with kzalloc so no data can leak apart from previous readings.
Note that previously no data could leak 'including' previous readings
but I don't think it is an issue to potentially leak them like
this now does.

In this case the postioning of the timestamp is depends on what
other channels are enabled. As such we cannot use a structure to
make the alignment explicit as it would be missleading by suggesting
only one possible location for the timestamp.

Fixes: 815bbc87462a ("iio: ti-adc0832: add triggered buffer support")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
 drivers/iio/adc/ti-adc0832.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

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diff --git a/drivers/iio/adc/ti-adc0832.c b/drivers/iio/adc/ti-adc0832.c
index c7a085dce1f4..71d49f97ab9c 100644
--- a/drivers/iio/adc/ti-adc0832.c
+++ b/drivers/iio/adc/ti-adc0832.c
@@ -29,6 +29,8 @@  struct adc0832 {
 	struct regulator *reg;
 	struct mutex lock;
 	u8 mux_bits;
+	/* 16x 1 byte ADC data + 8 bytes timestamp */
+	u8 data[24] __aligned(8);
 	u8 tx_buf[2] ____cacheline_aligned;
 	u8 rx_buf[2];
@@ -200,7 +202,6 @@  static irqreturn_t adc0832_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct adc0832 *adc = iio_priv(indio_dev);
-	u8 data[24] = { }; /* 16x 1 byte ADC data + 8 bytes timestamp */
 	int scan_index;
 	int i = 0;
@@ -218,10 +219,10 @@  static irqreturn_t adc0832_trigger_handler(int irq, void *p)
 			goto out;
-		data[i] = ret;
+		adc->data[i] = ret;
-	iio_push_to_buffers_with_timestamp(indio_dev, data,
+	iio_push_to_buffers_with_timestamp(indio_dev, adc->data,