linux-kernel - Re: backlight: catch invalid input

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Message-Id: <20081121155421.152cc555.akpm@linux-foundation.org>
Date:	Fri, 21 Nov 2008 15:54:21 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pavel Machek <pavel@...e.cz>
Cc:	rpurdie@...ys.net, linux-kernel@...r.kernel.org
Subject: Re: backlight: catch invalid input

On Fri, 21 Nov 2008 12:14:14 +0100
Pavel Machek <pavel@...e.cz> wrote:

> 
> Currently, echo > brightness turns brightness to zero due to
> insufficient checking. Add a test to catch that.
> 

OK.  And what happens if you do

	echo wibble > brightness

?

> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index fab0bc8..5c2e23d 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -86,6 +86,8 @@ static ssize_t backlight_store_power(str
>  	int power = simple_strtoul(buf, &endp, 0);
>  	size_t size = endp - buf;
>  
> +	if (!size)
> +		return -EINVAL;
>  	if (*endp && isspace(*endp))
>  		size++;
>  	if (size != count)

A better fix would be to use strict_strtoul() and check its return value.
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