From: Michal Nazarewicz <mina86@mina86.com>
To: Chuansheng Liu <chuansheng.liu@intel.com>, balbi@ti.com,
        gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        david.a.cohen@intel.com, jin.can.zhuang@intel.com, yu.y.wang@intel.com,
        Chuansheng Liu <chuansheng.liu@intel.com>
Subject: Re: [PATCH] usb: gadget: return the right length in ffs_epfile_io()
In-Reply-To: <1393483771-24623-1-git-send-email-chuansheng.liu@intel.com>
Organization: http://mina86.com/
References: <1393483771-24623-1-git-send-email-chuansheng.liu@intel.com>
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Date: Thu, 27 Feb 2014 13:15:25 +0100
Message-ID: <xa1teh2o4uqq.fsf@mina86.com>
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Sender: linux-kernel-owner@vger.kernel.org

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

Acked-by: Michal Nazarewicz <mina86@mina86.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 =3D ep->status;
> -			if (read && ret > 0 &&
> -			    unlikely(copy_to_user(buf, data,
> -						  min_t(size_t, ret, len))))
> -				ret =3D -EFAULT;
> +			if (read && ret > 0) {
> +				ret =3D min_t(size_t, ret, len);
> +
> +				if (unlikely(copy_to_user(buf, data, ret)))
> +					ret =3D -EFAULT;
> +			}
>  		}
>  	}
>=20=20
> --=20
> 1.9.rc0
>

--=20
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=3D./ `o
..o | Computer Science,  Micha=C5=82 =E2=80=9Cmina86=E2=80=9D Nazarewicz   =
 (o o)
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