USB: serial: io_edgeport: fix epic endpoint lookup

Make sure to use the current alternate setting when looking up the
endpoints on epic devices to avoid binding to an invalid interface.

Failing to do so could cause the driver to misbehave or trigger a WARN()
in usb_submit_urb() that kernels with panic_on_warn set would choke on.

Fixes: 6e8cf7751f9f ("USB: add EPIC support to the io_edgeport driver")
Cc: stable <stable@vger.kernel.org>     # 2.6.21
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191210112601.3561-5-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 48a439298a68fa8533df50f6e65f0aa7809c1b18..9690a5f4b9d611b26680f767310e5bcc34892b5c 100644 (file)
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -2901,16 +2901,18 @@ static int edge_startup(struct usb_serial *serial)
        response = 0;
 
        if (edge_serial->is_epic) {
+               struct usb_host_interface *alt;
+
+               alt = serial->interface->cur_altsetting;
+
                /* EPIC thing, set up our interrupt polling now and our read
                 * urb, so that the device knows it really is connected. */
                interrupt_in_found = bulk_in_found = bulk_out_found = false;
-               for (i = 0; i < serial->interface->altsetting[0]
-                                               .desc.bNumEndpoints; ++i) {
+               for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
                        struct usb_endpoint_descriptor *endpoint;
                        int buffer_size;
 
-                       endpoint = &serial->interface->altsetting[0].
-                                                       endpoint[i].desc;
+                       endpoint = &alt->endpoint[i].desc;
                        buffer_size = usb_endpoint_maxp(endpoint);
                        if (!interrupt_in_found &&
                            (usb_endpoint_is_int_in(endpoint))) {