[PATCH] iio: pressure: bmp280: zero-init bmp580 trigger handler buffer

[David Carlier <devnexen@gmail.com>]

bmp580_trigger_handler() builds an on-stack scan buffer containing
two __le32 fields and an aligned_s64 timestamp, and pushes it to
userspace via iio_push_to_buffers_with_ts(). However, only the low
3 bytes of each __le32 field are populated by the device data:

	memcpy(&buffer.comp_press, &data->buf[3], 3);
	memcpy(&buffer.comp_temp,  &data->buf[0], 3);

The high byte of each field is left uninitialised on the stack.
The bmp580 channels declare storagebits = 32, so the IIO core
transports all four bytes per sample to userspace as part of the
scan element, leaking two bytes of kernel stack per scan.

Zero-initialise the buffer before populating it, mirroring the fix
applied to bme280_trigger_handler() in commit 018f50909e66 ("iio:
bmp280: zero-init buffer").

Fixes: 872c8014e05e ("iio: pressure: bmp280: drop sensor_data array")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 drivers/iio/pressure/bmp280-core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index f37f20776c89..431476cff883 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -2623,6 +2623,8 @@ static irqreturn_t bmp580_trigger_handler(int irq, void *p)
 	} buffer;
 	int ret;
 
+	memset(&buffer, 0, sizeof(buffer));
+
 	guard(mutex)(&data->lock);
 
 	/* Burst read data registers */
-- 
2.53.0