| Message ID | 20200607155408.958437-19-jic23@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | IIO: Fused set 1 and 2 of timestamp alignment fixes | expand |
On Sun, Jun 07, 2020 at 04:53:54PM +0100, Jonathan Cameron wrote: > 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. > 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 array in the iio_priv() data with alignment > explicitly requested. This data is allocated with kzalloc so no > data can leak apart from previous readings. > + /* Ensure natural alignment for timestamp if present */ > + __le16 buf[16] __aligned(8); Perhaps struct in all such cases, like struct scan { __le16 buf[3 * 3]; // 3 axis per 3 sensors s64 ts; __aligned(8); }; ?
On Mon, 8 Jun 2020 16:17:12 +0300 Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > On Sun, Jun 07, 2020 at 04:53:54PM +0100, Jonathan Cameron wrote: > > 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. > > 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 array in the iio_priv() data with alignment > > explicitly requested. This data is allocated with kzalloc so no > > data can leak apart from previous readings. > > > + /* Ensure natural alignment for timestamp if present */ > > + __le16 buf[16] __aligned(8); > > Perhaps struct in all such cases, like > > struct scan { > __le16 buf[3 * 3]; // 3 axis per 3 sensors > s64 ts; __aligned(8); > }; > > ? > I did that for all the cases where the timestamp could only appear in one location, which are those with 8 bytes or less of channels + any which don't have flexible channel configs. Unfortunately that's not always the case in this driver. It depends on how many channels are turned on. As they are 2 bytes each, if you have only 1-4 channels enabled, then the timestamp will start at 8 bytes in. If you have 5-8 channels enabled it'll be 8 bytes in, if you have 9 channels it will be 24 bytes in. I thought about just ignoring that and pretending the timestamp was always in the same place but my thought was that we'd be implying something false and weird bugs lie down that sort of route. We could in theory do union { struct { __le16 buf[3 * 3]; s64 ts __aligned(8) }; struct { __le16 buf[4]; s64 ts __aligned(8); } short1; struct { __le16 buf[8]; s64 ts __aligned(8); } short2; } scan; But I guess you can see why I didn't go that route. Jonathan
diff --git a/drivers/iio/imu/bmi160/bmi160.h b/drivers/iio/imu/bmi160/bmi160.h index a82e040bd109..d29f1b5d1658 100644 --- a/drivers/iio/imu/bmi160/bmi160.h +++ b/drivers/iio/imu/bmi160/bmi160.h @@ -10,6 +10,8 @@ struct bmi160_data { struct iio_trigger *trig; struct regulator_bulk_data supplies[2]; struct iio_mount_matrix orientation; + /* Ensure natural alignment for timestamp if present */ + __le16 buf[16] __aligned(8); }; extern const struct regmap_config bmi160_regmap_config; diff --git a/drivers/iio/imu/bmi160/bmi160_core.c b/drivers/iio/imu/bmi160/bmi160_core.c index 222ebb26f013..86cfd75ea125 100644 --- a/drivers/iio/imu/bmi160/bmi160_core.c +++ b/drivers/iio/imu/bmi160/bmi160_core.c @@ -427,7 +427,6 @@ static irqreturn_t bmi160_trigger_handler(int irq, void *p) struct iio_poll_func *pf = p; struct iio_dev *indio_dev = pf->indio_dev; struct bmi160_data *data = iio_priv(indio_dev); - __le16 buf[16]; /* 3 sens x 3 axis x __le16 + 3 x __le16 pad + 4 x __le16 tstamp */ int i, ret, j = 0, base = BMI160_REG_DATA_MAGN_XOUT_L; __le16 sample; @@ -438,10 +437,10 @@ static irqreturn_t bmi160_trigger_handler(int irq, void *p) &sample, sizeof(sample)); if (ret) goto done; - buf[j++] = sample; + data->buf[j++] = sample; } - iio_push_to_buffers_with_timestamp(indio_dev, buf, pf->timestamp); + iio_push_to_buffers_with_timestamp(indio_dev, data->buf, pf->timestamp); done: iio_trigger_notify_done(indio_dev->trig); return IRQ_HANDLED;