[PATCH 4.8 013/138] gpio: GPIO_GET_LINEEVENT_IOCTL: Validate line offset

[Greg Kroah-Hartman]

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

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

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

commit b8b0e3d303654b3bb7b31b0266c513fd6f4132ce upstream.

The line offset that is used as an index into the descs array is provided
by userspace and might go beyond the bounds of the array. If that happens
undefined behavior will occur.

Make sure that the offset is within the bounds of the desc array and reject
any requests that specify a value outside of it.

Fixes: 61f922db7221 ("gpio: userspace ABI for reading GPIO line events")
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 |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -731,6 +731,11 @@ static int lineevent_create(struct gpio_
 	lflags = eventreq.handleflags;
 	eflags = eventreq.eventflags;
 
+	if (offset >= gdev->ngpio) {
+		ret = -EINVAL;
+		goto out_free_label;
+	}
+
 	/* This is just wrong: we don't look for events on output lines */
 	if (lflags & GPIOHANDLE_REQUEST_OUTPUT) {
 		ret = -EINVAL;