cdc-acm: fix possible invalid access when processing notification

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>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 00d55ba8983f..cdabe76960bc 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -323,6 +323,12 @@ 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;
+                }
+
                 newctrl = get_unaligned_le16(data);
 
                 if (!acm->clocal && (acm->ctrlin & ~newctrl & ACM_CTRL_DCD)) {
@@ -359,11 +365,10 @@ 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: