From e6a87f147002fa16adcbafebbc458ff90a463474 Mon Sep 17 00:00:00 2001

From: Oliver Neukum <oneukum@suse.com>

Date: Tue, 15 Mar 2016 10:14:04 +0100

Subject: [PATCH] cdc-acm: more sanity checking

An attack has become available which pretends to be a quirky

device circumventing normal sanity checks and crashes the kernel

by an insufficient number of interfaces. This patch adds a check

to the code path for quirky devices.

Signed-off-by: Oliver Neukum <ONeukum@suse.com>

CC: stable@vger.kernel.org

---

 drivers/usb/class/cdc-acm.c | 3 +++

 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c

index 26ca4f910cb0..a7732f80a912 100644

--- a/drivers/usb/class/cdc-acm.c

+++ b/drivers/usb/class/cdc-acm.c

@@ -1113,6 +1113,9 @@ static int acm_probe(struct usb_interface *intf,

 	if (quirks == NO_UNION_NORMAL) {

 		data_interface = usb_ifnum_to_if(usb_dev, 1);

 		control_interface = usb_ifnum_to_if(usb_dev, 0);

+		/* we would crash */

+		if (!data_interface || !control_interface)

+			return -ENODEV;

 		goto skip_normal_probe;

 	}

-- 

2.5.0