USB: serial: io_edgeport: fix epic endpoint lookup

commit 7c5a2df3367a2c4984f1300261345817d95b71f8 upstream.

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 de61271f2ba3a16279cca85251cfbce61ccd398e..e5649adcc84c49fd9beb0644319d6d7ce3a06499 100644 (file)
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -2852,16 +2852,18 @@ 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))) {