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

Fabio M. De Francesco
2021-08-24T15:07:05Z

On Tuesday, August 24, 2021 9:01:23 AM CEST Pavel Skripkin wrote:
> 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 the use of the new API I think that you don't have anymore
partial messages. usb_control_msg() returns the number of bytes
transferred, while usb_control_msg_recv/send return only 0 if successful
otherwise a negative error number.

Regards,

Fabio

> With regards,
> Pavel Skripkin
>