[PATCH 3.16.y-ckt 02/17] Input: powermate - fix oops with malicious USB descriptors

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

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

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

From: Josh Boyer <jwboyer@fedoraproject.org>

commit 9c6ba456711687b794dcf285856fc14e2c76074f upstream.

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

The full report for this issue can be found here:
http://seclists.org/bugtraq/2016/Mar/85

Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
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/powermate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/input/misc/powermate.c b/drivers/input/misc/powermate.c
index 63b539d3daba..84909a12ff36 100644
--- a/drivers/input/misc/powermate.c
+++ b/drivers/input/misc/powermate.c
@@ -307,6 +307,9 @@ static int powermate_probe(struct usb_interface *intf, const struct usb_device_i
 	int error = -ENOMEM;
 
 	interface = intf->cur_altsetting;
+	if (interface->desc.bNumEndpoints < 1)
+		return -EINVAL;
+
 	endpoint = &interface->endpoint[0].desc;
 	if (!usb_endpoint_is_int_in(endpoint))
 		return -EIO;