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Subject[PATCH v3 1/4] cdc-acm: fix possible invalid access when processing notification
Date
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>
---
drivers/usb/class/cdc-acm.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index e35b150..f554e2f 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -322,6 +322,12 @@ 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)) {
@@ -358,11 +364,10 @@ 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:
--
2.1.4
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