linux-kernel - Re: [PATCH 2/3] serial: add helpers to copy serial

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Date:   Fri, 26 Aug 2022 18:42:10 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>
Subject: Re: [PATCH 2/3] serial: add helpers to copy serial_rs485 from/to userspace

On Fri, Aug 26, 2022 at 5:51 PM Ilpo Järvinen
<ilpo.jarvinen@...ux.intel.com> wrote:
>
> Due to the padding fields, the copying will need to a bit more than
> usual.
>
> Move padding clearing into the helper that copies back to userspace.

If you agree on the below and address as suggested,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  drivers/tty/serial/serial_core.c | 41 +++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 9c1bf36b7a93..6d57cfdeda9d 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1375,10 +1375,6 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
>         rs485->flags &= supported_flags;
>
>         uart_sanitize_serial_rs485_delays(port, rs485);
> -
> -       /* Return clean padding area to userspace */
> -       memset(rs485->padding0, 0, sizeof(rs485->padding0));
> -       memset(rs485->padding1, 0, sizeof(rs485->padding1));
>  }
>
>  static void uart_set_rs485_termination(struct uart_port *port,
> @@ -1407,6 +1403,28 @@ int uart_rs485_config(struct uart_port *port)
>  }
>  EXPORT_SYMBOL_GPL(uart_rs485_config);
>
> +static int user_rs485_to_kernel_serial_rs485(struct serial_rs485 *rs485,
> +                                            const struct serial_rs485 __user *rs485_user)

What about

serial_rs485_from_user()

> +{
> +       if (copy_from_user(rs485, rs485_user, sizeof(*rs485)))
> +               return -EFAULT;
> +
> +       return 0;
> +}
> +
> +static int kernel_serial_rs485_to_user_rs485(struct serial_rs485 __user *rs485_user,
> +                                            struct serial_rs485 *rs485)

serial_rs485_to_user()

?

> +{
> +       /* Return clean padding area to userspace */
> +       memset(rs485->padding0, 0, sizeof(rs485->padding0));
> +       memset(rs485->padding1, 0, sizeof(rs485->padding1));
> +
> +       if (copy_to_user(rs485_user, rs485, sizeof(*rs485)))
> +               return -EFAULT;
> +
> +       return 0;
> +}
> +
>  static int uart_get_rs485_config(struct uart_port *port,
>                          struct serial_rs485 __user *rs485_user)
>  {
> @@ -1417,10 +1435,7 @@ static int uart_get_rs485_config(struct uart_port *port,
>         rs485 = port->rs485;
>         spin_unlock_irqrestore(&port->lock, flags);
>
> -       if (copy_to_user(rs485_user, &rs485, sizeof(rs485)))
> -               return -EFAULT;
> -
> -       return 0;
> +       return kernel_serial_rs485_to_user_rs485(rs485_user, &rs485);
>  }
>
>  static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
> @@ -1433,8 +1448,9 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
>         if (!port->rs485_config)
>                 return -ENOTTY;
>
> -       if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
> -               return -EFAULT;
> +       ret = user_rs485_to_kernel_serial_rs485(&rs485, rs485_user);
> +       if (ret)
> +               return ret;
>
>         ret = uart_check_rs485_flags(port, &rs485);
>         if (ret)
> @@ -1450,10 +1466,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
>         if (ret)
>                 return ret;
>
> -       if (copy_to_user(rs485_user, &port->rs485, sizeof(port->rs485)))
> -               return -EFAULT;
> -
> -       return 0;
> +       return kernel_serial_rs485_to_user_rs485(rs485_user, &port->rs485);
>  }
>
>  static int uart_get_iso7816_config(struct uart_port *port,
> --
> 2.30.2
>


-- 
With Best Regards,
Andy Shevchenko