linux-kernel - Re: [PATCH 5/9] staging: panel: check put

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Message-ID: <20100730211544.GH19782@1wt.eu>
Date:	Fri, 30 Jul 2010 23:15:44 +0200
From:	Willy Tarreau <w@....eu>
To:	Kulikov Vasiliy <segooon@...il.com>
Cc:	kernel-janitors@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Peter Huewe <peterhuewe@....de>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Julia Lawall <julia@...u.dk>, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] staging: panel: check put_user() return value

On Fri, Jul 30, 2010 at 03:08:42PM +0400, Kulikov Vasiliy wrote:
> diff --git a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
> index f58da32..57f4946 100644
> --- a/drivers/staging/panel/panel.c
> +++ b/drivers/staging/panel/panel.c
> @@ -1589,25 +1589,30 @@ void lcd_init(void)
>  static ssize_t keypad_read(struct file *file,
>  			   char *buf, size_t count, loff_t *ppos)
>  {
> -
> +	int buflen = keypad_buflen;
>  	unsigned i = *ppos;
>  	char *tmp = buf;
> +	int start = keypad_start;
>  
> -	if (keypad_buflen == 0) {
> +	if (buflen == 0) {
>  		if (file->f_flags & O_NONBLOCK)
>  			return -EAGAIN;
>  
>  		interruptible_sleep_on(&keypad_read_wait);
>  		if (signal_pending(current))
>  			return -EINTR;
> +		buflen = keypad_buflen;
>  	}

Not sure what the intent was here, I think you're re-adjusting
the buffer's length in case something else was read. But then
I don't understand why buflen it not simply assigned after the
if() block.

The rest below looks fine otherwise.

>  
> -	for (; count-- > 0 && (keypad_buflen > 0);
> -	     ++i, ++tmp, --keypad_buflen) {
> -		put_user(keypad_buffer[keypad_start], tmp);
> -		keypad_start = (keypad_start + 1) % KEYPAD_BUFFER;
> +	for (; count-- > 0 && (buflen > 0);
> +	     ++i, ++tmp, --buflen) {
> +		if (put_user(keypad_buffer[start], tmp))
> +			return -EFAULT;
> +		start = (start + 1) % KEYPAD_BUFFER;
>  	}
>  	*ppos = i;
> +	keypad_buflen = buflen;
> +	keypad_start = start;
>  
>  	return tmp - buf;
>  }


Regards,
Willy

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