linux-kernel - Re: [PATCH v2 1/4] serial: Rename vars in uart_get_rs485

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Message-ID: <Yw3QMI0m2X/8aL7z@kroah.com>
Date:   Tue, 30 Aug 2022 10:54:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v2 1/4] serial: Rename vars in uart_get_rs485_config()

On Tue, Aug 30, 2022 at 10:29:53AM +0300, Ilpo Järvinen wrote:
> Make variable names to match uart_set_rs485_config() ones:
> 	- rs485 -> rs485_user
> 	- aux -> rs485
> 
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  drivers/tty/serial/serial_core.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 12c87cd201a7..8834414a0b2f 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1408,16 +1408,16 @@ int uart_rs485_config(struct uart_port *port)
>  EXPORT_SYMBOL_GPL(uart_rs485_config);
>  
>  static int uart_get_rs485_config(struct uart_port *port,
> -			 struct serial_rs485 __user *rs485)
> +			 struct serial_rs485 __user *rs485_user)
>  {
> +	struct serial_rs485 rs485;
>  	unsigned long flags;
> -	struct serial_rs485 aux;
>  
>  	spin_lock_irqsave(&port->lock, flags);
> -	aux = port->rs485;
> +	rs485 = port->rs485;
>  	spin_unlock_irqrestore(&port->lock, flags);

I missed this originally, but why does the lock matter here at all?  You
are just copying all data out of the structure into an on-stack one, why
the extra step at all?

As the structure can change instantly after you release the lock, I
don't see what the lock is protecting.

thanks,

greg k-h