staging: comedi: check validity of wMaxPacketSize of usb endpoints found

While finding usb endpoints in vmk80xx_find_usb_endpoints(), check if
wMaxPacketSize = 0 for the endpoints found.

Some devices have isochronous endpoints that have wMaxPacketSize = 0
(as required by the USB-2 spec).
However, since this doesn't apply here, wMaxPacketSize = 0 can be
considered to be invalid.

Reported-by: syzbot+009f546aa1370056b1c2@syzkaller.appspotmail.com
Tested-by: syzbot+009f546aa1370056b1c2@syzkaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201010082933.5417-1-anant.thazhemadam@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/vmk80xx.c b/drivers/staging/comedi/drivers/vmk80xx.c
index 65dc6c5..7956abc 100644 (file)
--- a/drivers/staging/comedi/drivers/vmk80xx.c
+++ b/drivers/staging/comedi/drivers/vmk80xx.c
@@ -667,6 +667,9 @@ static int vmk80xx_find_usb_endpoints(struct comedi_device *dev)
        if (!devpriv->ep_rx || !devpriv->ep_tx)
                return -ENODEV;
 
+       if (!usb_endpoint_maxp(devpriv->ep_rx) || !usb_endpoint_maxp(devpriv->ep_tx))
+               return -EINVAL;
+
        return 0;
 }