iio: adc: ti-ads8688: fix information leak in triggered buffer

BugLink: https://bugs.launchpad.net/bugs/2106770

commit 2a7377c upstream.

The 'buffer' local array 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.

Initialize the array to zero before using it to avoid pushing
uninitialized information to userspace.

Cc: stable@vger.kernel.org
Fixes: 61fa5df ("iio: adc: ti-ads8688: Fix alignment of buffer in iio_push_to_buffers_with_timestamp()")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20241125-iio_memset_scan_holes-v1-8-0cb6e98d895c@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE-2024-57906
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

Author: javiercarrascocruz

drivers/iio/adc/ti-ads8688.c

@@ -382,7 +382,7 @@ static irqreturn_t ads8688_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	/* Ensure naturally aligned timestamp */
-	u16 buffer[ADS8688_MAX_CHANNELS + sizeof(s64)/sizeof(u16)] __aligned(8);
+	u16 buffer[ADS8688_MAX_CHANNELS + sizeof(s64)/sizeof(u16)] __aligned(8) = { };
 	int i, j = 0;
 
 	for (i = 0; i < indio_dev->masklength; i++) {