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    Subject[PATCH 5.10 679/717] iio:magnetometer:mag3110: Fix alignment and data leak issues.
    Date
    From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

    commit 89deb1334252ea4a8491d47654811e28b0790364 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 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 not necessary in this case but
    does make the code slightly less fragile so I have included it.

    Fixes: 39631b5f9584 ("iio: Add Freescale mag3110 magnetometer driver")
    Reported-by: Lars-Peter Clausen <lars@metafoo.de>
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
    Cc: <Stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/20200920112742.170751-4-jic23@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/iio/magnetometer/mag3110.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    --- a/drivers/iio/magnetometer/mag3110.c
    +++ b/drivers/iio/magnetometer/mag3110.c
    @@ -56,6 +56,12 @@ struct mag3110_data {
    int sleep_val;
    struct regulator *vdd_reg;
    struct regulator *vddio_reg;
    + /* Ensure natural alignment of timestamp */
    + struct {
    + __be16 channels[3];
    + u8 temperature;
    + s64 ts __aligned(8);
    + } scan;
    };

    static int mag3110_request(struct mag3110_data *data)
    @@ -387,10 +393,9 @@ static irqreturn_t mag3110_trigger_handl
    struct iio_poll_func *pf = p;
    struct iio_dev *indio_dev = pf->indio_dev;
    struct mag3110_data *data = iio_priv(indio_dev);
    - u8 buffer[16]; /* 3 16-bit channels + 1 byte temp + padding + ts */
    int ret;

    - ret = mag3110_read(data, (__be16 *) buffer);
    + ret = mag3110_read(data, data->scan.channels);
    if (ret < 0)
    goto done;

    @@ -399,10 +404,10 @@ static irqreturn_t mag3110_trigger_handl
    MAG3110_DIE_TEMP);
    if (ret < 0)
    goto done;
    - buffer[6] = ret;
    + data->scan.temperature = ret;
    }

    - iio_push_to_buffers_with_timestamp(indio_dev, buffer,
    + iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
    iio_get_time_ns(indio_dev));

    done:

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