linux-kernel - Re: [PATCHv2 6/9] staging: vme_user: return -EFAULT on __copy_*

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Message-ID: <20150625112758.GB13366@sudip-PC>
Date:	Thu, 25 Jun 2015 16:57:58 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Dmitry Kalinkin <dmitry.kalinkin@...il.com>
Cc:	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	Martyn Welch <martyn.welch@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Manohar Vanga <manohar.vanga@...il.com>
Subject: Re: [PATCHv2 6/9] staging: vme_user: return -EFAULT on __copy_*_user
 errors

On Tue, Jun 23, 2015 at 07:03:36PM +0300, Dmitry Kalinkin wrote:
> Signed-off-by: Dmitry Kalinkin <dmitry.kalinkin@...il.com>
> ---
>  drivers/staging/vme/devices/vme_user.c | 47 ++++++++--------------------------
>  1 file changed, 11 insertions(+), 36 deletions(-)
> 
<snip>
> @@ -178,38 +167,24 @@ static ssize_t buffer_to_user(unsigned int minor, char __user *buf,
>  			      size_t count, loff_t *ppos)
>  {
>  	void *image_ptr;
> -	ssize_t retval;
>  
>  	image_ptr = image[minor].kern_buf + *ppos;
> +	if (__copy_to_user(buf, image_ptr, (unsigned long)count))
> +		return -EFAULT;
>  
> -	retval = __copy_to_user(buf, image_ptr, (unsigned long)count);
> -	if (retval != 0) {
> -		retval = (count - retval);
> -		pr_warn("Partial copy to userspace\n");
> -	} else
> -		retval = count;
> -
> -	/* Return number of bytes successfully read */
> -	return retval;
> +	return count;
will it not affect the userspace code?
previously number of bytes successfully read was returned, now incase of
partial read -EFAULT is being returned.

regards
sudip
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