On 22/05/06 03:12PM, Pavel Skripkin wrote: > Hi Wang, > > On 5/6/22 14:59, Wang Cheng wrote: > > Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@xxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Wang Cheng <wanngchenng@xxxxxxxxx> > > --- > > drivers/staging/rtl8712/usb_ops.c | 27 ++++++++++++++++++--------- > > 1 file changed, 18 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/staging/rtl8712/usb_ops.c b/drivers/staging/rtl8712/usb_ops.c > > index e64845e6adf3..af9966d03979 100644 > > --- a/drivers/staging/rtl8712/usb_ops.c > > +++ b/drivers/staging/rtl8712/usb_ops.c > > @@ -29,7 +29,8 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr) > > u16 wvalue; > > u16 index; > > u16 len; > > - __le32 data; > > + int status; > > + __le32 data = 0; > > struct intf_priv *intfpriv = intfhdl->pintfpriv; > > request = 0x05; > > @@ -37,8 +38,10 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr) > > index = 0; > > wvalue = (u16)(addr & 0x0000ffff); > > len = 1; > > - r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len, > > - requesttype); > > + status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, > > + &data, len, requesttype); > > + if (status < 0) > > + return 0; > > Wait, but what about partial reads? I see that r8712_usbctrl_vendorreq() > uses `usb_control_msg()` which can read less data than was requested. > > So here you are just hiding these error by zeroing data > > > return (u8)(le32_to_cpu(data) & 0x0ff); > > } > > And as i said in previous email: caller can't see an error. > > Imagine caller waits for some register to become 0. Caller sees that > usb_read8() returned 0. Is it an error? Is register really become 0? > > > Generic read API prototype looks like following: > > int read_something(struct my_cool_dev *dev, void *data, size_t size); > > and it returns 0 on success and -errno on failure and data returned via > passed pointer. So, if API returned an error caller should not touch @data, > since likely it's uninitialized Thank you for your remind, sorry I didnt understand your previous reply about "register and 0" that you explain very clearly above. I am thinking about it standing on that the return type of usb_read8() is u8. thanks, - w
