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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>,
        "Vladis Dronov" <vdronov@redhat.com>,
        "Dmitry Torokhov" <dmitry.torokhov@gmail.com>
Date:   Fri, 24 Apr 2020 00:06:39 +0100
Message-ID: <lsq.1587683028.552896285@decadent.org.uk>
Subject: [PATCH 3.16 172/245] Input: aiptek - fix endpoint sanity check
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 3111491fca4f01764e0c158c5e0f7ced808eef51 upstream.

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: 8e20cf2bce12 ("Input: aiptek - fix crash on detecting device without endpoints")
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Vladis Dronov <vdronov@redhat.com>
Link: https://lore.kernel.org/r/20191210113737.4016-3-johan@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/input/tablet/aiptek.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/input/tablet/aiptek.c
+++ b/drivers/input/tablet/aiptek.c
@@ -1820,14 +1820,14 @@ aiptek_probe(struct usb_interface *intf,
 	input_set_abs_params(inputdev, ABS_WHEEL, AIPTEK_WHEEL_MIN, AIPTEK_WHEEL_MAX - 1, 0, 0);
 
 	/* Verify that a device really has an endpoint */
-	if (intf->altsetting[0].desc.bNumEndpoints < 1) {
+	if (intf->cur_altsetting->desc.bNumEndpoints < 1) {
 		dev_err(&intf->dev,
 			"interface has %d endpoints, but must have minimum 1\n",
-			intf->altsetting[0].desc.bNumEndpoints);
+			intf->cur_altsetting->desc.bNumEndpoints);
 		err = -EINVAL;
 		goto fail3;
 	}
-	endpoint = &intf->altsetting[0].endpoint[0].desc;
+	endpoint = &intf->cur_altsetting->endpoint[0].desc;
 
 	/* Go set up our URB, which is called when the tablet receives
 	 * input.