iio:gyro:itg3200: Fix timestamp alignment and prevent data leak.

commit 10ab7cfd5522f0041028556dac864a003e158556 upstream.

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 array of smaller elements on the stack.
This is fixed by using an explicit c structure. As there are no
holes in the structure, there is no possiblity of data leakage
in this case.

The explicit alignment of ts is not strictly necessary but potentially
makes the code slightly less fragile.  It also removes the possibility
of this being cut and paste into another driver where the alignment
isn't already true.

Fixes: 36e0371e7764 ("iio:itg3200: Use iio_push_to_buffers_with_timestamp()")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200722155103.979802-6-jic23@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/gyro/itg3200_buffer.c b/drivers/iio/gyro/itg3200_buffer.c
index 59770e5b66602cb8eeb92241a3e22b3b20a91b11..b080362a876695df360b11db63106f61c1792194 100644 (file)
--- a/drivers/iio/gyro/itg3200_buffer.c
+++ b/drivers/iio/gyro/itg3200_buffer.c
@@ -49,13 +49,20 @@ static irqreturn_t itg3200_trigger_handler(int irq, void *p)
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct itg3200 *st = iio_priv(indio_dev);
-       __be16 buf[ITG3200_SCAN_ELEMENTS + sizeof(s64)/sizeof(u16)];
-
-       int ret = itg3200_read_all_channels(st->i2c, buf);
+       /*
+        * Ensure correct alignment and padding including for the
+        * timestamp that may be inserted.
+        */
+       struct {
+               __be16 buf[ITG3200_SCAN_ELEMENTS];
+               s64 ts __aligned(8);
+       } scan;
+
+       int ret = itg3200_read_all_channels(st->i2c, scan.buf);
        if (ret < 0)
                goto error_ret;
 
-       iio_push_to_buffers_with_timestamp(indio_dev, buf, pf->timestamp);
+       iio_push_to_buffers_with_timestamp(indio_dev, &scan, pf->timestamp);
 
        iio_trigger_notify_done(indio_dev->trig);