linux-kernel - Re: [PATCH] tty/serial_core: Introduce lock mechanism for RS485

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Message-ID: <20141013145229.4849f07a@alan.etchedpixels.co.uk>
Date:	Mon, 13 Oct 2014 14:52:29 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH] tty/serial_core: Introduce lock mechanism for RS485

> @@ -1154,8 +1154,16 @@ static int uart_get_icount(struct tty_struct *tty,
>  static int uart_get_rs485_config(struct uart_port *port,
>  			 struct serial_rs485 __user *rs485)
>  {
> -	if (copy_to_user(rs485, &port->rs485, sizeof(port->rs485)))
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	ret = copy_to_user(rs485, &port->rs485, sizeof(port->rs485));
> +	spin_unlock_irqrestore(&port->lock, flags);

Looks good apart from this bit.. The copy needs to go to a temporary
before the lock is taken otherwise we may sleep on a pagefault with irqs
off

Alan
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