[PATCH] USB: s2255 & stkwebcam: fix oops with malicious USB descriptors

[Young Xiao <92siuyang@gmail.com>]

From: Young Xiao <YangX92@hotmail.com>

The driver expects at least one valid endpoint. If given
malicious descriptors that specify 0 for the number of endpoints,
it will crash in the probe function.  Ensure there is at least
one endpoint on the interface before using it.

This vulnerability is same as CVE-2016-2188.

Signed-off-by: Young Xiao <YangX92@hotmail.com>
---
 drivers/media/usb/s2255/s2255drv.c       | 7 +++++++
 drivers/media/usb/stkwebcam/stk-webcam.c | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/drivers/media/usb/s2255/s2255drv.c b/drivers/media/usb/s2255/s2255drv.c
index 5b3e54b..82dd661 100644
--- a/drivers/media/usb/s2255/s2255drv.c
+++ b/drivers/media/usb/s2255/s2255drv.c
@@ -2263,6 +2263,13 @@ static int s2255_probe(struct usb_interface *interface,
 	iface_desc = interface->cur_altsetting;
 	dev_dbg(&interface->dev, "num EP: %d\n",
 		iface_desc->desc.bNumEndpoints);
+
+	if (iface_desc->desc.bNumEndpoints < 1) {
+		dev_err(&interface->dev, "Invalid number of endpoints\n");
+		retval = -EINVAL;
+		goto errorEP;
+	}
+
 	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 		endpoint = &iface_desc->endpoint[i].desc;
 		if (!dev->read_endpoint && usb_endpoint_is_bulk_in(endpoint)) {
diff --git a/drivers/media/usb/stkwebcam/stk-webcam.c b/drivers/media/usb/stkwebcam/stk-webcam.c
index 8f54586..e427c3d 100644
--- a/drivers/media/usb/stkwebcam/stk-webcam.c
+++ b/drivers/media/usb/stkwebcam/stk-webcam.c
@@ -1350,6 +1350,12 @@ static int stk_camera_probe(struct usb_interface *interface,
 	 * for the current alternate setting */
 	iface_desc = interface->cur_altsetting;
 
+	if (iface_desc->desc.bNumEndpoints < 1) {
+		dev_err(&interface->dev, "Invalid number of endpoints\n");
+		err = -EINVAL;
+		goto error;
+	}
+
 	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 		endpoint = &iface_desc->endpoint[i].desc;
 
-- 
1.9.1