[PATCH 4.8 012/138] gpio: GPIOHANDLE_GET_LINE_VALUES_IOCTL: Fix information leak

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

commit 3eded5d83bf4e36ad78775c7ceb44a45480b0abd upstream.

The GPIOHANDLE_GET_LINE_VALUES_IOCTL handler allocates a gpiohandle_data
struct on the stack and then passes it to copy_to_user(). But depending on
the number of requested line handles the struct is only partially
initialized.

This exposes the previous, potentially sensitive, stack content to the
issuing userspace application. To avoid this make sure that the struct is
fully initialized.

Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpio/gpiolib.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -342,6 +342,8 @@ static long linehandle_ioctl(struct file
 	if (cmd == GPIOHANDLE_GET_LINE_VALUES_IOCTL) {
 		int val;
 
+		memset(&ghd, 0, sizeof(ghd));
+
 		/* TODO: check if descriptors are really input */
 		for (i = 0; i < lh->numdescs; i++) {
 			val = gpiod_get_value_cansleep(lh->descs[i]);