linux-kernel - Re: [PATCH 08/10] staging: r8188eu: clean up the usb

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Message-ID: <20210822165844.2h6yt42ejshw7tnc@viti.kaiser.cx>
Date:   Sun, 22 Aug 2021 18:58:44 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Michael Straube <straube.linux@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] staging: r8188eu: clean up the usb_writeN

Hi Michael,

Thus wrote Michael Straube (straube.linux@...il.com):

> On 8/21/21 6:48 PM, Martin Kaiser wrote:
> > Remove unnecessary variables, check the length.

> > Signed-off-by: Martin Kaiser <martin@...ser.cx>
> > ---
> >   drivers/staging/r8188eu/hal/usb_ops_linux.c | 15 +++++----------
> >   1 file changed, 5 insertions(+), 10 deletions(-)

> > diff --git a/drivers/staging/r8188eu/hal/usb_ops_linux.c b/drivers/staging/r8188eu/hal/usb_ops_linux.c
> > index e01f1ac19596..5408383ccec3 100644
> > --- a/drivers/staging/r8188eu/hal/usb_ops_linux.c
> > +++ b/drivers/staging/r8188eu/hal/usb_ops_linux.c
> > @@ -151,20 +151,15 @@ static int usb_write32(struct intf_hdl *pintfhdl, u32 addr, u32 val)
> >   static int usb_writeN(struct intf_hdl *pintfhdl, u32 addr, u32 length, u8 *pdata)
> >   {
> > -	u16 wvalue;
> > -	u16 len;
> > +	u16 wvalue = (u16)(addr & 0x0000ffff);
> >   	u8 buf[VENDOR_CMD_MAX_DATA_LEN] = {0};
> > -	int ret;
> > -
> > +	if (length > VENDOR_CMD_MAX_DATA_LEN)
> > +		return -EINVAL;
> > -	wvalue = (u16)(addr & 0x0000ffff);
> > -	len = length;
> > -	memcpy(buf, pdata, len);
> > +	memcpy(buf, pdata, length);

> Hi Martin, shouldn't this be

> memcpy(buf, pdata, (length & 0xffff));

I don't think this makes any difference. I've already checked that
length <= VENDOR_CMD_MAX_DATA_LEN, which is 254. memcpy takes a size_t
parameter for the number of bytes to copy. length will not overflow
this.

Best regards,
Martin