Make sure to verify the number of ports requested by subdriver to avoid
writing beyond the end of fixed-size array in interface data.

The current usb-serial implementation is limited to eight ports per
interface but failed to verify that the number of ports requested by a
subdriver (which could have been determined from device descriptors) did
not exceed this limit.

Cc: stable <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
---
 drivers/usb/serial/usb-serial.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index eb0e8c6a8682..475723c006f9 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -862,6 +862,11 @@ static int usb_serial_probe(struct usb_interface 
*interface,
                        num_ports = type->num_ports;
        }
 
+       if (num_ports > MAX_NUM_PORTS) {
+               dev_warn(ddev, "too many ports requested: %d\n", num_ports);
+               num_ports = MAX_NUM_PORTS;
+       }
+
        serial->num_ports = num_ports;
        serial->num_bulk_in = num_bulk_in;
        serial->num_bulk_out = num_bulk_out;
-- 
1.8.5.5

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