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Subject[PATCH v2 2/4] cdc-acm: fix possible invalid access when processing notification
Date
Notifications may only be 8 bytes so 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 | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 74acca1..a7c8878 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -296,6 +296,12 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
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)) {
@@ -332,11 +338,10 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)

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->wLength);
}
}

--
2.1.4
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