USB: serial: io_edgeport: fix epic endpoint lookup

BugLink: https://bugs.launchpad.net/bugs/1857158
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 17283f4b4779719f0d7092febbc2649052bf595b..ae1a73e5d962050e5c01f39d5da5b24974dee63f 100644 (file)
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -2914,16 +2914,18 @@ 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))) {