[PATCH] usbip: fix vudc_rx: harden CMD_SUBMIT path to handle malicious input

[Shuah Khan]

Harden CMD_SUBMIT path to handle malicious input that could trigger
large memory allocations. Add checks to validate transfer_buffer_length
and number_of_packets to protect against bad input requesting for
unbounded memory allocations.

Signed-off-by: Shuah Khan <shua...@osg.samsung.com>
---
 drivers/usb/usbip/vudc_rx.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/usb/usbip/vudc_rx.c b/drivers/usb/usbip/vudc_rx.c
index df1e30989148..1e8a23d92cb4 100644
--- a/drivers/usb/usbip/vudc_rx.c
+++ b/drivers/usb/usbip/vudc_rx.c
@@ -120,6 +120,25 @@ static int v_recv_cmd_submit(struct vudc *udc,
        urb_p->new = 1;
        urb_p->seqnum = pdu->base.seqnum;
 
+       if (urb_p->ep->type == USB_ENDPOINT_XFER_ISOC) {
+               /* validate packet size and number of packets */
+               unsigned int maxp, packets, bytes;
+
+               maxp = usb_endpoint_maxp(urb_p->ep->desc);
+               maxp *= usb_endpoint_maxp_mult(urb_p->ep->desc);
+               bytes = pdu->u.cmd_submit.transfer_buffer_length;
+               packets = DIV_ROUND_UP(bytes, maxp);
+
+               if (pdu->u.cmd_submit.number_of_packets < 0 ||
+                   pdu->u.cmd_submit.number_of_packets > packets) {
+                       dev_err(&udc->gadget.dev,
+                               "CMD_SUBMIT: isoc invalid num packets %d\n",
+                               pdu->u.cmd_submit.number_of_packets);
+                       ret = -EMSGSIZE;
+                       goto free_urbp;
+               }
+       }
+
        ret = alloc_urb_from_cmd(&urb_p->urb, pdu, urb_p->ep->type);
        if (ret) {
                usbip_event_add(&udc->ud, VUDC_EVENT_ERROR_MALLOC);
-- 
2.14.1