[PATCH 04/11][CVE-2016-2186] Input: powermate - fix oops with malicious USB descriptors

[Luis Henriques]

From: Josh Boyer <jwboyer at 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 at spenneberg.net>
Signed-off-by: Josh Boyer <jwboyer at fedoraproject.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
CVE-2016-2186
BugLink: https://bugs.launchpad.net/bugs/1561411
Signed-off-by: Luis Henriques <luis.henriques at 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 f45947190e4f..be34cd6a5030 100644
--- a/drivers/input/misc/powermate.c
+++ b/drivers/input/misc/powermate.c
@@ -304,6 +304,9 @@ 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;