Android 使用的某些 Linux 内核版本受到 CVE-2021-39685 问题的影响。有关 CVE-2021-39685 的详细信息和 POC 可在 inspector-gadget 仓库中找到。
本仓库包含了针对多个 Android 特定 USB gadget 的 POC，包括：
a) f_accessory
int acc_ctrlrequest(struct usb_composite_dev *cdev,
const struct usb_ctrlrequest *ctrl)
{
struct acc_dev *dev = get_acc_dev();
int value = -EOPNOTSUPP;
struct acc_hid_dev *hid;
int offset;
u8 b_requestType = ctrl->bRequestType;
u8 b_request = ctrl->bRequest;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
unsigned long flags;
...
if (b_requestType == (USB_DIR_OUT | USB_TYPE_VENDOR)) {
...
} else if (b_request == ACCESSORY_SEND_STRING) {
dev_info(&cdev->gadget->dev, "%s: got ACCESSORY_SEND_STRING(52) request\n",
__func__);
schedule_work(&dev->sendstring_work);
dev->string_index = w_index;
cdev->gadget->ep0->driver_data = dev;
cdev->req->complete = acc_complete_set_string;
value = w_length;
...
} else if (b_request == ACCESSORY_SEND_HID_EVENT) {
spin_lock_irqsave(&dev->lock, flags);
hid = acc_hid_get(&dev->hid_list, w_value);
spin_unlock_irqrestore(&dev->lock, flags);
if (!hid) {
value = -EINVAL;
goto err;
}
cdev->req->context = hid;
cdev->req->complete = acc_complete_send_hid_event;
value = w_length;
}
...
if (value >= 0) {
cdev->req->zero = 0;
cdev->req->length = value;
value = usb_ep_queue(cdev->gadget->ep0, cdev->req, GFP_ATOMIC);
if (value < 0)
ERROR(cdev, "%s setup response queue error\n",
__func__);
}
b) f_audio_source
static int
audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct usb_composite_dev *cdev = f->config->cdev;
struct usb_request *req = cdev->req;
int value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
/* composite driver infrastructure handles everything; interface
* activation uses set_alt().
*/
switch (ctrl->bRequestType) {
case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
value = audio_set_endpoint_req(f, ctrl);
break;
case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
value = audio_get_endpoint_req(f, ctrl);
break;
}
/* respond with data transfer or status phase? */
if (value >= 0) {
pr_debug("audio req%02x.%02x v%04x i%04x l%d\n",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->zero = 0;
req->length = value;
req->complete = audio_control_complete;
value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (value < 0)
pr_err("audio response on err %d\n", value);
}
static int audio_set_endpoint_req(struct usb_function *f,
const struct usb_ctrlrequest *ctrl)
{
int value = -EOPNOTSUPP;
u16 ep = le16_to_cpu(ctrl->wIndex);
u16 len = le16_to_cpu(ctrl->wLength);
u16 w_value = le16_to_cpu(ctrl->wValue);
pr_debug("bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
ctrl->bRequest, w_value, len, ep);
switch (ctrl->bRequest) {
case UAC_SET_CUR:
case UAC_SET_MIN:
case UAC_SET_MAX:
case UAC_SET_RES:
value = len;
break;
default:
break;
}
return value;
}
c) f_gsi
static int
gsi_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct f_gsi *gsi = func_to_gsi(f);
struct usb_composite_dev *cdev = f->config->cdev;
struct usb_request *req = cdev->req;
int id, value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
struct gsi_ctrl_pkt *cpkt;
u8 *buf;
u32 n;
bool line_state;
...
switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
...
case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
| USB_CDC_SEND_ENCAPSULATED_COMMAND:
log_event_dbg("USB_CDC_SEND_ENCAPSULATED_COMMAND");
if (w_value || w_index != id)
goto invalid;
/* read the request; process it later */
value = w_length;
req->context = gsi;
if (gsi->prot_id == IPA_USB_RNDIS)
req->complete = gsi_rndis_command_complete;
else
req->complete = gsi_ctrl_cmd_complete;
/* later, rndis_response_available() sends a notification */
break;
...
...
/* respond with data transfer or status phase? */
if (value >= 0) {
log_event_dbg("req%02x.%02x v%04x i%04x l%d",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->zero = (value < w_length);
req->length = value;
value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (value < 0)
log_event_err("response on err %d", value);
}
d) f_mtp
static int mtp_ctrlrequest(struct usb_composite_dev *cdev,
const struct usb_ctrlrequest *ctrl)
{
struct mtp_dev *dev = _mtp_dev;
int value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
unsigned long flags;
...
} else if ((ctrl->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS) {
mtp_log("class request: %d index: %d value: %d length: %d\n",
ctrl->bRequest, w_index, w_value, w_length);
if (ctrl->bRequest == MTP_REQ_CANCEL && w_index == 0
&& w_value == 0) {
mtp_log("MTP_REQ_CANCEL\n");
spin_lock_irqsave(&dev->lock, flags);
if (dev->state == STATE_BUSY) {
dev->state = STATE_CANCELED;
wake_up(&dev->read_wq);
wake_up(&dev->write_wq);
}
spin_unlock_irqrestore(&dev->lock, flags);
/* We need to queue a request to read the remaining
* bytes, but we don't actually need to look at
* the contents.
*/
value = w_length;
...
/* respond with data transfer or status phase? */
if (value >= 0) {
int rc;
cdev->req->zero = value < w_length;
cdev->req->length = value;
rc = usb_ep_queue(cdev->gadget->ep0, cdev->req, GFP_ATOMIC);
if (rc < 0)
pr_err("%s: response queue error\n", __func__);
}
e) f_qc_rndis