Re: [PATCH] mct_u232: sanity checking in probe

[Johan Hovold <johan@kernel.org>]

On Wed, Mar 16, 2016 at 02:23:33PM +0100, Oliver Neukum wrote:
> An attack using the lack of sanity checking in probe
> is known. This patch checks for the existance of a
> second port.
> CVE-2016-3136
> 
> Signed-off-by: Oliver Neukum <ONeukum@suse.com>
> CC: stable@vger.kernel.org
> ---
>  drivers/usb/serial/mct_u232.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
> index fd707d6..d6a36b1 100644
> --- a/drivers/usb/serial/mct_u232.c
> +++ b/drivers/usb/serial/mct_u232.c
> @@ -378,6 +378,10 @@ static int mct_u232_port_probe(struct usb_serial_port *port)
>  {
>  	struct mct_u232_private *priv;
>  
> +	/* check first to simplify error handling */
> +	if (!port->serial->port[1])
> +		return -ENODEV;
> +

This check is not sufficient as the second port's interrupt-in urb is
also unconditionally dereferenced below. Care to fix that up?

Ideally the existence of a second interrupt-in urb should have been
verified already at interface probe. But we can clean that up later.

>  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
>  	if (!priv)
>  		return -ENOMEM;

Thanks,
Johan