Re: stack leak via uart_get_info() ?

From: Greg Kroah-Hartman
Date: Thu Oct 05 2023 - 13:56:12 EST


On Thu, Oct 05, 2023 at 07:34:21PM +0300, Alexey Dobriyan wrote:
> If this check ever triggers
>
> static int uart_get_info(struct tty_port *port, struct serial_struct *retinfo)
> {
>
> uport = uart_port_check(state);
> if (!uport)
> goto out;
>
> then all those sysfs users will print stack contents to userspace.
>
> Can it trigger while sysfs read is executing?

I don't think it can ever fail, we don't even check the result in other
places, so it should all be fine.

> Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> ---
>
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -775,6 +775,8 @@ static int uart_get_info(struct tty_port *port, struct serial_struct *retinfo)
> struct uart_port *uport;
> int ret = -ENODEV;
>
> + *retinfo = (struct serial_struct){};

This is good (although I hate the implied memcpy), a real memset would
be best to ensure that any holes are also filled. Want to do that, or
want me to?

thanks,

greg k-h