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iio:accel:mma8452: Fix timestamp alignment and prevent data leak.

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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 a 16 byte u8 array 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 with alignment
ensured by use of an explicit c structure.  This data is allocated
with kzalloc so no data can leak appart from previous readings.

The additional forcing of the 8 byte alignment of the timestamp
is not strictly necessary but makes the code less fragile by
making this explicit.

Fixes: c7eeea93ac ("iio: Add Freescale MMA8452Q 3-axis accelerometer driver")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>
This commit is contained in:
Jonathan Cameron 2020-07-22 16:50:38 +01:00
parent 95ad67577d
commit 89226a296d
1 changed files with 8 additions and 3 deletions
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11
drivers/iio/accel/mma8452.c
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@ -110,6 +110,12 @@ struct mma8452_data {
int sleep_val;
struct regulator *vdd_reg;
struct regulator *vddio_reg;
/* Ensure correct alignment of time stamp when present */
struct {
__be16 channels[3];
s64 ts __aligned(8);
} buffer;
};
/**
@ -1091,14 +1097,13 @@ static irqreturn_t mma8452_trigger_handler(int irq, void *p)
struct iio_poll_func *pf = p;
struct iio_dev *indio_dev = pf->indio_dev;
struct mma8452_data *data = iio_priv(indio_dev);
u8 buffer[16]; /* 3 16-bit channels + padding + ts */
int ret;
ret = mma8452_read(data, (__be16 *)buffer);
ret = mma8452_read(data, data->buffer.channels);
if (ret < 0)
goto done;
iio_push_to_buffers_with_timestamp(indio_dev, buffer,
iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
iio_get_time_ns(indio_dev));
done: