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

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Message-ID: <xa1teh2o4uqq.fsf@mina86.com>
Date:	Thu, 27 Feb 2014 13:15:25 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Chuansheng Liu <chuansheng.liu@...el.com>, balbi@...com,
	gregkh@...uxfoundation.org
Cc:	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, Chuansheng Liu <chuansheng.liu@...el.com>
Subject: Re: [PATCH] usb: gadget: return the right length in ffs_epfile_io()

On Thu, Feb 27 2014, Chuansheng Liu <chuansheng.liu@...el.com> 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>

Acked-by: Michal Nazarewicz <mina86@...a86.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;
> +			}
>  		}
>  	}
>  
> -- 
> 1.9.rc0
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--


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