[PATCH 3.16 019/134] cdc-acm: fix possible invalid access when processing notification

Ben Hutchings
2017-08-18T13:15:42Z

From: Tobias Herzog <t-herzog@gmx.de>

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/class/cdc-acm.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -312,6 +312,12 @@ 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)) {
@@ -348,11 +354,10 @@ 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;
}