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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, Denis Kirjanov <kda@linux-powerpc.org>,
        "Johan Hovold" <johan@kernel.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
Date:   Fri, 24 Apr 2020 00:05:13 +0100
Message-ID: <lsq.1587683028.548461089@decadent.org.uk>
Subject: [PATCH 3.16 086/245] USB: serial: io_edgeport: fix epic endpoint
 lookup
In-Reply-To: <lsq.1587683027.831233700@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@kernel.org>

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")
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: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/usb/serial/io_edgeport.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -2859,16 +2859,18 @@ static int edge_startup(struct usb_seria
 	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))) {