Re: [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32

[Pavel Skripkin]

On 8/24/21 9:58 AM, Dan Carpenter wrote:
> On Sun, Aug 22, 2021 at 05:36:01PM +0300, Pavel Skripkin wrote:
> > -static u32 usb_read32(struct intf_hdl *pintfhdl, u32 addr)
> > +static int usb_read32(struct intf_hdl *pintfhdl, u32 addr, u32 *data)
> >  {
> >  	u8 requesttype;
> >  	u16 wvalue;
> >  	u16 len;
> > -	__le32 data;
> > +	int res;
> > +	__le32 tmp;
> > +
> > +	if (WARN_ON(unlikely(!data)))
> > +		return -EINVAL;
> >  
> >  	requesttype = 0x01;/* read_in */
> >  
> >  	wvalue = (u16)(addr & 0x0000ffff);
> >  	len = 4;
> >  
> > -	usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype);
> > +	res = usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype);
> > +	if (res < 0) {
> > +		dev_err(dvobj_to_dev(pintfhdl->pintf_dev), "Failed to read 32 bytes: %d\n", res);
>
> Add a return here.  Try to keep the success path and the failure path
> as separate as possible.  Try to keep the success path indented at one
> tab so the code looks like this:
>
> 	success();
> 	success();
> 	if (fail)
> 		handle_failure();
> 	success();
> 	success();
>
> Try to deal with exceptions as quickly as possible so that the reader
> has less to remember.
>
> > +	} else {
> > +		/* Noone cares about positive return value */
>
> Ugh...  That's unfortunate.  We should actually care.  The
> usbctrl_vendorreq() has an information leak where it copies len (4)
> bytes of data even if usb_control_msg() is not able to read len bytes.
>
> The best fix would be to remove the information leak and make
> usbctrl_vendorreq() return zero on success.  In other words something
> like:
>
> 	status = usb_control_msg();
> 	if (status < 0)
> 		return status;
> 	if (status != len)
> 		return -EIO;
> 	status = 0;

I see, thank you for reviewing, will fix in v3! I fully forgot, that 
usb_control_msg() can receive only part of the message :)



With regards,
Pavel Skripkin