Commit db8f06d9 authored by Jonathan Cameron's avatar Jonathan Cameron

iio:adc:max1118 Fix alignment of timestamp and data leak issues

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() data.

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

The explicit alignment of ts is necessary to ensure correct padding
on architectures where s64 is only 4 bytes aligned such as x86_32.

Fixes: a9e9c715 ("iio: adc: add max1117/max1118/max1119 ADC driver")
Reported-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>
parent f8cd222f
...@@ -36,6 +36,11 @@ struct max1118 { ...@@ -36,6 +36,11 @@ struct max1118 {
struct spi_device *spi; struct spi_device *spi;
struct mutex lock; struct mutex lock;
struct regulator *reg; struct regulator *reg;
/* Ensure natural alignment of buffer elements */
struct {
u8 channels[2];
s64 ts __aligned(8);
} scan;
u8 data ____cacheline_aligned; u8 data ____cacheline_aligned;
}; };
...@@ -166,7 +171,6 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p) ...@@ -166,7 +171,6 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p)
struct iio_poll_func *pf = p; struct iio_poll_func *pf = p;
struct iio_dev *indio_dev = pf->indio_dev; struct iio_dev *indio_dev = pf->indio_dev;
struct max1118 *adc = iio_priv(indio_dev); struct max1118 *adc = iio_priv(indio_dev);
u8 data[16] = { }; /* 2x 8-bit ADC data + padding + 8 bytes timestamp */
int scan_index; int scan_index;
int i = 0; int i = 0;
...@@ -184,10 +188,10 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p) ...@@ -184,10 +188,10 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p)
goto out; goto out;
} }
data[i] = ret; adc->scan.channels[i] = ret;
i++; i++;
} }
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)); iio_get_time_ns(indio_dev));
out: out:
mutex_unlock(&adc->lock); mutex_unlock(&adc->lock);
......
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