Re: [PATCH 1/2] USB: serial: console: fix use-after-free on disconnect

[Andrey Konovalov]

On Wed, Oct 4, 2017 at 11:01 AM, Johan Hovold <johan@xxxxxxxxxx> wrote:
> A clean-up patch removing removing two redundant NULL-checks from the
> console disconnect handler inadvertently also removed a third check.
> This could lead to the struct usb_serial being prematurely freed by the
> console code when a driver accepts but does not register any ports for
> an interface which also lacks endpoint descriptors.
>
> Fixes: 0e517c93dc02 ("USB: serial: console: clean up sanity checks")
> Cc: stable <stable@xxxxxxxxxxxxxxx>     # 4.11
> Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

This fixes the crash.

Thanks!

> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> ---
>  drivers/usb/serial/console.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/serial/console.c b/drivers/usb/serial/console.c
> index fdf89800ebc3..ed8ba3ef5c79 100644
> --- a/drivers/usb/serial/console.c
> +++ b/drivers/usb/serial/console.c
> @@ -265,7 +265,7 @@ static struct console usbcons = {
>
>  void usb_serial_console_disconnect(struct usb_serial *serial)
>  {
> -       if (serial->port[0] == usbcons_info.port) {
> +       if (serial->port[0] && serial->port[0] == usbcons_info.port) {
>                 usb_serial_console_exit();
>                 usb_serial_put(serial);
>         }
> --
> 2.14.2
>