linux-kernel - [PATCH 4/7] Input: gtco: fix endpoint sanity check

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Date:   Tue, 10 Dec 2019 12:37:34 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        stable <stable@...r.kernel.org>,
        Vladis Dronov <vdronov@...hat.com>
Subject: [PATCH 4/7] Input: gtco: fix endpoint sanity check

The driver was checking the number of endpoints of the first alternate
setting instead of the current one, something which could lead to the
driver binding to an invalid interface.

This in turn 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: 162f98dea487 ("Input: gtco - fix crash on detecting device without endpoints")
Cc: stable <stable@...r.kernel.org>     # 4.6
Cc: Vladis Dronov <vdronov@...hat.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/input/tablet/gtco.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
index 35031228a6d0..799c94dda651 100644
--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -875,18 +875,14 @@ static int gtco_probe(struct usb_interface *usbinterface,
 	}
 
 	/* Sanity check that a device has an endpoint */
-	if (usbinterface->altsetting[0].desc.bNumEndpoints < 1) {
+	if (usbinterface->cur_altsetting->desc.bNumEndpoints < 1) {
 		dev_err(&usbinterface->dev,
 			"Invalid number of endpoints\n");
 		error = -EINVAL;
 		goto err_free_urb;
 	}
 
-	/*
-	 * The endpoint is always altsetting 0, we know this since we know
-	 * this device only has one interrupt endpoint
-	 */
-	endpoint = &usbinterface->altsetting[0].endpoint[0].desc;
+	endpoint = &usbinterface->cur_altsetting->endpoint[0].desc;
 
 	/* Some debug */
 	dev_dbg(&usbinterface->dev, "gtco # interfaces: %d\n", usbinterface->num_altsetting);
@@ -973,7 +969,7 @@ static int gtco_probe(struct usb_interface *usbinterface,
 	input_dev->dev.parent = &usbinterface->dev;
 
 	/* Setup the URB, it will be posted later on open of input device */
-	endpoint = &usbinterface->altsetting[0].endpoint[0].desc;
+	endpoint = &usbinterface->cur_altsetting->endpoint[0].desc;
 
 	usb_fill_int_urb(gtco->urbinfo,
 			 udev,
-- 
2.24.0