cdc-acm: fix possible invalid access when processing notification

commit 1bb9914e1730417d530de9ed37e59efdc647146b upstream.

Notifications may only be 8 bytes long. Accessing the 9th and
10th byte of unimplemented/unknown notifications may be insecure.
Also check the length of known notifications before accessing anything
behind the 8th byte.

Signed-off-by: Tobias Herzog <t-herzog@gmx.de>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 93249aa..210b533 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -293,6 +293,12 @@ static void acm_ctrl_irq(struct urb *urb)
                break;
 
        case USB_CDC_NOTIFY_SERIAL_STATE:
+               if (le16_to_cpu(dr->wLength) != 2) {
+                       dev_dbg(&acm->control->dev,
+                               "%s - malformed serial state\n", __func__);
+                       break;
+               }
+
                tty = tty_port_tty_get(&acm->port);
                newctrl = get_unaligned_le16(data);
 
@@ -323,11 +329,10 @@ static void acm_ctrl_irq(struct urb *urb)
 
        default:
                dev_dbg(&acm->control->dev,
-                       "%s - unknown notification %d received: index %d "
-                       "len %d data0 %d data1 %d\n",
+                       "%s - unknown notification %d received: index %d len %d\n",
                        __func__,
-                       dr->bNotificationType, dr->wIndex,
-                       dr->wLength, data[0], data[1]);
+                       dr->bNotificationType, dr->wIndex, dr->wLength);
+
                break;
        }
 exit: