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

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Date:   Mon, 9 Oct 2017 13:05:30 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] USB: serial: console: fix use-after-free on disconnect

On Wed, Oct 4, 2017 at 11:01 AM, Johan Hovold <johan@...nel.org> 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@...r.kernel.org>     # 4.11
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>

Tested-by: Andrey Konovalov <andreyknvl@...gle.com>

This fixes the crash.

Thanks!

> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
>  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
>