linux-kernel - Re: [PATCH] usb: gadget: return the right length in ffs_epfile

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Date:	Mon, 3 Mar 2014 10:30:13 -0600
From:	Felipe Balbi <balbi@...com>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
CC:	<balbi@...com>, <gregkh@...uxfoundation.org>, <mina86@...a86.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<david.a.cohen@...el.com>, <jin.can.zhuang@...el.com>,
	<yu.y.wang@...el.com>
Subject: Re: [PATCH] usb: gadget: return the right length in ffs_epfile_io()

Hi,

On Thu, Feb 27, 2014 at 02:49:31PM +0800, Chuansheng Liu wrote:
> When the request length is aligned to maxpacketsize, sometimes
> the return length ret > the user space requested len.
> 
> At that time, we will use min_t(size_t, ret, len) to limit the
> size in case of user data buffer overflow.
> 
> But we need return the min_t(size_t, ret, len) to tell the user
> space rightly also.
> 
> Signed-off-by: Chuansheng Liu <chuansheng.liu@...el.com>
> ---
>  drivers/usb/gadget/f_fs.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
> index 2b43343..31ee7af 100644
> --- a/drivers/usb/gadget/f_fs.c
> +++ b/drivers/usb/gadget/f_fs.c
> @@ -687,10 +687,12 @@ static ssize_t ffs_epfile_io(struct file *file,
>  			 * space for.
>  			 */
>  			ret = ep->status;
> -			if (read && ret > 0 &&
> -			    unlikely(copy_to_user(buf, data,
> -						  min_t(size_t, ret, len))))
> -				ret = -EFAULT;
> +			if (read && ret > 0) {
> +				ret = min_t(size_t, ret, len);
> +
> +				if (unlikely(copy_to_user(buf, data, ret)))
> +					ret = -EFAULT;
> +			}

please rebase on my "testing/next" branch

-- 
balbi

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