Re: [PATCH v3 4/6] staging: r8188eu: add error handling of rtw_read16

Fabio M. De Francesco
2021-08-25T04:35:11Z

On Tuesday, August 24, 2021 9:27:35 AM CEST Pavel Skripkin wrote:
> _rtw_read16 function can fail in case of usb transfer failure. But
> previous function prototype wasn't designed to return an error to
> caller. It can cause a lot uninit value bugs all across the driver code,
> since rtw_read16() returns local stack variable to caller.
>
> Fix it by changing the prototype of this function. Now it returns an
> int: 0 on success, negative error value on failure and callers should pass
> the pointer to storage location for register value.
>
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
>
> [...]
>
> -static u16 usb_read16(struct intf_hdl *pintfhdl, u32 addr)
> +static int usb_read16(struct intf_hdl *pintfhdl, u32 addr, u16 *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 = 2;
> - usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype);
> + res = usbctrl_vendorreq(pintfhdl, wvalue, &tmp, len, requesttype);
> + if (res < 0) {
> + dev_err(dvobj_to_dev(pintfhdl->pintf_dev), "Failed to read 16 bytes: %d\n", res);
> + return res;
> + } else if (res != len) {

Dear Pavel,

Please note that if and when my patch "Use usb_control_msg_recv / send () in
usbctrl_vendorreq ()" will be merged, "if (res! = len)" will always evaluate 'true'
and usb_read16 () will always return -EIO even if usbctrl_vendorreq () succeeds.

> + dev_err(dvobj_to_dev(pintfhdl->pintf_dev),
> + "Failed to read 16 bytes, could read only %d bytes\n", res);
> + return -EIO;
> + }
>
> - return (u16)(le32_to_cpu(data) & 0xffff);
> + *data = le32_to_cpu(tmp) & 0xffff;
> +
> + return 0;
> }

[...]

Regards,

Fabio