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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johan Hovold <johan@kernel.org>,
        Martin Kepplinger <martink@posteo.de>,
        Vladis Dronov <vdronov@redhat.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: [PATCH 4.9 255/271] Input: pegasus_notetaker - fix endpoint sanity check
Date:   Tue, 28 Jan 2020 15:06:44 +0100
Message-Id: <20200128135911.576746222@linuxfoundation.org>
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From: Johan Hovold <johan@kernel.org>

commit bcfcb7f9b480dd0be8f0df2df17340ca92a03b98 upstream.

The driver was checking the number of endpoints of the first alternate
setting instead of the current one, something which could be used by a
malicious device (or USB descriptor fuzzer) to trigger a NULL-pointer
dereference.

Fixes: 1afca2b66aac ("Input: add Pegasus Notetaker tablet driver")
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Martin Kepplinger <martink@posteo.de>
Acked-by: Vladis Dronov <vdronov@redhat.com>
Link: https://lore.kernel.org/r/20191210113737.4016-2-johan@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/input/tablet/pegasus_notetaker.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/input/tablet/pegasus_notetaker.c
+++ b/drivers/input/tablet/pegasus_notetaker.c
@@ -260,7 +260,7 @@ static int pegasus_probe(struct usb_inte
 		return -ENODEV;
 
 	/* Sanity check that the device has an endpoint */
-	if (intf->altsetting[0].desc.bNumEndpoints < 1) {
+	if (intf->cur_altsetting->desc.bNumEndpoints < 1) {
 		dev_err(&intf->dev, "Invalid number of endpoints\n");
 		return -EINVAL;
 	}