diff mbox series

[07/32] iio:chemical:ccs811: Fix timestamp alignment and prevent data leak.

Message ID 20200607155408.958437-8-jic23@kernel.org (mailing list archive)
State New, archived
Headers show
Series IIO: Fused set 1 and 2 of timestamp alignment fixes | expand

Commit Message

Jonathan Cameron June 7, 2020, 3:53 p.m. UTC 
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 structure in the iio_priv() data with alignment
explicitly requested.  This data is allocated with kzalloc so no
data can leak appart from previous readings.

The explicit alignment of ts is necessary to ensure consistent
padding for x86_32 in which the ts would otherwise be 4 byte aligned.

Fixes: 283d26917ad6 ("iio: chemical: ccs811: Add triggered buffer support")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Narcisa Ana Maria Vasile <narcisaanamaria12@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/chemical/ccs811.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c
index 2b007e7568b2..60dd87e96f5f 100644
--- a/drivers/iio/chemical/ccs811.c
+++ b/drivers/iio/chemical/ccs811.c
@@ -78,6 +78,11 @@  struct ccs811_data {
 	struct iio_trigger *drdy_trig;
 	struct gpio_desc *wakeup_gpio;
 	bool drdy_trig_on;
+	/* Ensures correct alignment of timestamp if present */
+	struct {
+		s16 channels[2];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 static const struct iio_chan_spec ccs811_channels[] = {
@@ -327,17 +332,17 @@  static irqreturn_t ccs811_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct ccs811_data *data = iio_priv(indio_dev);
 	struct i2c_client *client = data->client;
-	s16 buf[8]; /* s16 eCO2 + s16 TVOC + padding + 8 byte timestamp */
 	int ret;
 
-	ret = i2c_smbus_read_i2c_block_data(client, CCS811_ALG_RESULT_DATA, 4,
-					    (u8 *)&buf);
+	ret = i2c_smbus_read_i2c_block_data(client, CCS811_ALG_RESULT_DATA,
+					    sizeof(data->scan.channels),
+					    (u8 *)data->scan.channels);
 	if (ret != 4) {
 		dev_err(&client->dev, "cannot read sensor data\n");
 		goto err;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buf,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   iio_get_time_ns(indio_dev));
 
 err: