USB: serial: fix potential stack buffer overflow

Make sure to verify the maximum number of endpoints per type to avoid
writing beyond the end of a stack-allocated array.

The current usb-serial implementation is limited to eight ports per
interface but failed to verify that the number of endpoints of a certain
type reported by a device did not exceed this limit.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/usb-serial.c

@@ -764,29 +764,39 @@ static int usb_serial_probe(struct usb_interface *interface,
 		if (usb_endpoint_is_bulk_in(endpoint)) {
 			/* we found a bulk in endpoint */
 			dev_dbg(ddev, "found bulk in on endpoint %d\n", i);
-			bulk_in_endpoint[num_bulk_in] = endpoint;
-			++num_bulk_in;
+			if (num_bulk_in < MAX_NUM_PORTS) {
+				bulk_in_endpoint[num_bulk_in] = endpoint;
+				++num_bulk_in;
+			}
 		}
 
 		if (usb_endpoint_is_bulk_out(endpoint)) {
 			/* we found a bulk out endpoint */
 			dev_dbg(ddev, "found bulk out on endpoint %d\n", i);
-			bulk_out_endpoint[num_bulk_out] = endpoint;
-			++num_bulk_out;
+			if (num_bulk_out < MAX_NUM_PORTS) {
+				bulk_out_endpoint[num_bulk_out] = endpoint;
+				++num_bulk_out;
+			}
 		}
 
 		if (usb_endpoint_is_int_in(endpoint)) {
 			/* we found a interrupt in endpoint */
 			dev_dbg(ddev, "found interrupt in on endpoint %d\n", i);
-			interrupt_in_endpoint[num_interrupt_in] = endpoint;
-			++num_interrupt_in;
+			if (num_interrupt_in < MAX_NUM_PORTS) {
+				interrupt_in_endpoint[num_interrupt_in] =
+						endpoint;
+				++num_interrupt_in;
+			}
 		}
 
 		if (usb_endpoint_is_int_out(endpoint)) {
 			/* we found an interrupt out endpoint */
 			dev_dbg(ddev, "found interrupt out on endpoint %d\n", i);
-			interrupt_out_endpoint[num_interrupt_out] = endpoint;
-			++num_interrupt_out;
+			if (num_interrupt_out < MAX_NUM_PORTS) {
+				interrupt_out_endpoint[num_interrupt_out] =
+						endpoint;
+				++num_interrupt_out;
+			}
 		}
 	}
 
@@ -809,8 +819,10 @@ static int usb_serial_probe(struct usb_interface *interface,
 				if (usb_endpoint_is_int_in(endpoint)) {
 					/* we found a interrupt in endpoint */
 					dev_dbg(ddev, "found interrupt in for Prolific device on separate interface\n");
-					interrupt_in_endpoint[num_interrupt_in] = endpoint;
-					++num_interrupt_in;
+					if (num_interrupt_in < MAX_NUM_PORTS) {
+						interrupt_in_endpoint[num_interrupt_in] = endpoint;
+						++num_interrupt_in;
+					}
 				}
 			}
 		}