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

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

[Johan Hovold]

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@vger.kernel.org>     # 4.11
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Johan Hovold <johan@kernel.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

[PATCH 2/2] USB: serial: console: fix use-after-free after failed setup

[Johan Hovold]

Make sure to reset the USB-console port pointer when console setup fails
in order to avoid having the struct usb_serial be prematurely freed by
the console code when the device is later disconnected.

Fixes: 73e487fdb75f ("[PATCH] USB console: fix disconnection issues")
Cc: stable <stable@vger.kernel.org>	# 2.6.18
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/console.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/serial/console.c b/drivers/usb/serial/console.c
index ed8ba3ef5c79..43a862a90a77 100644
--- a/drivers/usb/serial/console.c
+++ b/drivers/usb/serial/console.c
@@ -186,6 +186,7 @@ static int usb_console_setup(struct console *co, char *options)
 	tty_kref_put(tty);
  reset_open_count:
 	port->port.count = 0;
+	info->port = NULL;
 	usb_autopm_put_interface(serial->interface);
  error_get_interface:
 	usb_serial_put(serial);
-- 
2.14.2

Re: [PATCH 2/2] USB: serial: console: fix use-after-free after failed setup

[Greg KH]

On Wed, Oct 04, 2017 at 11:01:13AM +0200, Johan Hovold wrote:
> Make sure to reset the USB-console port pointer when console setup fails
> in order to avoid having the struct usb_serial be prematurely freed by
> the console code when the device is later disconnected.
> 
> Fixes: 73e487fdb75f ("[PATCH] USB console: fix disconnection issues")
> Cc: stable <stable@vger.kernel.org>	# 2.6.18
> Signed-off-by: Johan Hovold <johan@kernel.org>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

[Greg KH]

On Wed, Oct 04, 2017 at 11:01:12AM +0200, Johan Hovold 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@vger.kernel.org>     # 4.11
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Johan Hovold <johan@kernel.org>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

[Jaejoong Kim]

Hi

2017-10-04 18:01 GMT+09:00 Johan Hovold <johan@kernel.org>:
> A clean-up patch removing removing two redundant NULL-checks from the
                               ^^^^^^^^^^^^^^^^^^
The word 'removing' was written twice. :)

> 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@vger.kernel.org>     # 4.11
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Johan Hovold <johan@kernel.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
>
> --
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Re: [PATCH 1/2] USB: serial: console: fix use-after-free on disconnect

[Johan Hovold]

On Sat, Oct 07, 2017 at 05:56:17PM +0900, Jaejoong Kim wrote:
> Hi
> 
> 2017-10-04 18:01 GMT+09:00 Johan Hovold <johan@kernel.org>:
> > A clean-up patch removing removing two redundant NULL-checks from the
>                                ^^^^^^^^^^^^^^^^^^
> The word 'removing' was written twice. :)

Thanks for noticing, now fixed up.

Johan

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@kernel.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@vger.kernel.org>     # 4.11
> Reported-by: Andrey Konovalov <andreyknvl@google.com>

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

This fixes the crash.

Thanks!

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

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

[Johan Hovold]

On Mon, Oct 09, 2017 at 01:05:30PM +0200, Andrey Konovalov wrote:
> On Wed, Oct 4, 2017 at 11:01 AM, Johan Hovold <johan@kernel.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@vger.kernel.org>     # 4.11
> > Reported-by: Andrey Konovalov <andreyknvl@google.com>
> 
> Tested-by: Andrey Konovalov <andreyknvl@google.com>
> 
> This fixes the crash.

I just forwarded this one in a pull-request to Greg, but thanks for
testing nonetheless.

Johan