linux-kernel - Re: divide by zero in termios when setting bluetooth

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Message-ID: <20091201160151.GD2262@elf.ucw.cz>
Date:	Tue, 1 Dec 2009 17:01:51 +0100
From:	Pavel Machek <pavel@....cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	linux-bluetooth@...r.kernel.org,
	Marcel Holtmann <marcel@...tmann.org>
Subject: Re: divide by zero in termios when setting bluetooth

Hi!

> > I triggered this by mistake... "W" taint is from the  WARN_ON()
> > before.
> 
> This ought to fix it
> 
> serial: Fix crash if the minimum rate of the device is > 9600 baud
> 
> From: Alan Cox <alan@...ux.intel.com>
> 
> In that situation if the old rate is invalid and the new rate is invalid
> and the chip cannot do 9600 baud we report zero, which makes all the
> drivers explode.
> 
> Instead force the rate based on min/max
> 
> Signed-off-by: Alan Cox <alan@...ux.intel.com>

>  		}
>  
>  		/*
> -		 * As a last resort, if the quotient is zero,
> -		 * default to 9600 bps
> +		 * As a last resort, if the range cannot be met then clip to
> +		 * the nearest chip supported rate.
>  		 */
> -		if (!hung_up)
> -			tty_termios_encode_baud_rate(termios, 9600, 9600);
> +		if (!hung_up) {
> +			if (baud <= min)                
> +				tty_termios_encode_baud_rate(termios,
> +							min + 1, min + 1);
> +			else
> +				tty_termios_encode_baud_rate(termios,
> +							max - 1, max - 1);
> +		}
>  	}
> -
> +	/* Should never happen */
> +	WARN_ON(1);
>  	return 0;

Does this mean WARN_ON() on user error? Maybe printk(KERN_ERR) with
explanation would be better?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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