iio: dummy: iio_simply_dummy_buffer: fix information leak in triggered buffer

BugLink: https://bugs.launchpad.net/bugs/2097298

commit 333be43 upstream.

The 'data' array is allocated via kmalloc() and it is used to push data
to user space from a triggered buffer, but it does not set values for
inactive channels, as it only uses iio_for_each_active_channel()
to assign new values.

Use kzalloc for the memory allocation to avoid pushing uninitialized
information to userspace.

Cc: stable@vger.kernel.org
Fixes: 415f792 ("iio: Move IIO Dummy Driver out of staging")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20241125-iio_memset_scan_holes-v1-9-0cb6e98d895c@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>

Author: javiercarrascocruz

drivers/iio/dummy/iio_simple_dummy_buffer.c

@@ -48,7 +48,7 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
 	int len = 0;
 	u16 *data;
 
-	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
+	data = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
 	if (!data)
 		goto done;