[PATCH 3.16.y-ckt 10/17] Input: ati_remote2 - fix crashes on detecting device with invalid descriptor

[Luis Henriques <luis.henriques@canonical.com>]

3.16.7-ckt27 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Vladis Dronov <vdronov@redhat.com>

commit 950336ba3e4a1ffd2ca60d29f6ef386dd2c7351d upstream.

The ati_remote2 driver expects at least two interfaces with one
endpoint each. If given malicious descriptor that specify one
interface or no endpoints, it will crash in the probe function.
Ensure there is at least two interfaces and one endpoint for each
interface before using it.

The full disclosure: http://seclists.org/bugtraq/2016/Mar/90

Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Moritz Muehlenhoff <jmm@inutil.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/input/misc/ati_remote2.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/input/misc/ati_remote2.c b/drivers/input/misc/ati_remote2.c
index f63341f20b91..e8c6a4842e91 100644
--- a/drivers/input/misc/ati_remote2.c
+++ b/drivers/input/misc/ati_remote2.c
@@ -817,26 +817,49 @@ static int ati_remote2_probe(struct usb_interface *interface, const struct usb_d
 
 	ar2->udev = udev;
 
+	/* Sanity check, first interface must have an endpoint */
+	if (alt->desc.bNumEndpoints < 1 || !alt->endpoint) {
+		dev_err(&interface->dev,
+			"%s(): interface 0 must have an endpoint\n", __func__);
+		r = -ENODEV;
+		goto fail1;
+	}
 	ar2->intf[0] = interface;
 	ar2->ep[0] = &alt->endpoint[0].desc;
 
+	/* Sanity check, the device must have two interfaces */
 	ar2->intf[1] = usb_ifnum_to_if(udev, 1);
+	if ((udev->actconfig->desc.bNumInterfaces < 2) || !ar2->intf[1]) {
+		dev_err(&interface->dev, "%s(): need 2 interfaces, found %d\n",
+			__func__, udev->actconfig->desc.bNumInterfaces);
+		r = -ENODEV;
+		goto fail1;
+	}
+
 	r = usb_driver_claim_interface(&ati_remote2_driver, ar2->intf[1], ar2);
 	if (r)
 		goto fail1;
+
+	/* Sanity check, second interface must have an endpoint */
 	alt = ar2->intf[1]->cur_altsetting;
+	if (alt->desc.bNumEndpoints < 1 || !alt->endpoint) {
+		dev_err(&interface->dev,
+			"%s(): interface 1 must have an endpoint\n", __func__);
+		r = -ENODEV;
+		goto fail2;
+	}
 	ar2->ep[1] = &alt->endpoint[0].desc;
 
 	r = ati_remote2_urb_init(ar2);
 	if (r)
-		goto fail2;
+		goto fail3;
 
 	ar2->channel_mask = channel_mask;
 	ar2->mode_mask = mode_mask;
 
 	r = ati_remote2_setup(ar2, ar2->channel_mask);
 	if (r)
-		goto fail2;
+		goto fail3;
 
 	usb_make_path(udev, ar2->phys, sizeof(ar2->phys));
 	strlcat(ar2->phys, "/input0", sizeof(ar2->phys));
@@ -845,11 +868,11 @@ static int ati_remote2_probe(struct usb_interface *interface, const struct usb_d
 
 	r = sysfs_create_group(&udev->dev.kobj, &ati_remote2_attr_group);
 	if (r)
-		goto fail2;
+		goto fail3;
 
 	r = ati_remote2_input_init(ar2);
 	if (r)
-		goto fail3;
+		goto fail4;
 
 	usb_set_intfdata(interface, ar2);
 
@@ -857,10 +880,11 @@ static int ati_remote2_probe(struct usb_interface *interface, const struct usb_d
 
 	return 0;
 
- fail3:
+ fail4:
 	sysfs_remove_group(&udev->dev.kobj, &ati_remote2_attr_group);
- fail2:
+ fail3:
 	ati_remote2_urb_cleanup(ar2);
+ fail2:
 	usb_driver_release_interface(&ati_remote2_driver, ar2->intf[1]);
  fail1:
 	kfree(ar2);