Re: [PATCH v3 5/6] staging: r8188eu: add error handling of rtw_read32

[Pavel Skripkin]

On 8/26/21 1:59 PM, David Laight wrote:
> From: Pavel Skripkin
> > Sent: 26 August 2021 11:55
> >
> > On 8/26/21 1:22 PM, David Laight wrote:
> > > From: Pavel Skripkin
> > >> Sent: 26 August 2021 10:28
> > >>
> > >> On 8/26/21 12:22 PM, Pavel Skripkin wrote:
> > >> > On Thu, 26 Aug 2021 08:51:23 +0000
> > >> > David Laight <David.Laight@xxxxxxxxxx> 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;
> > >> >> >
> > >> >>
> > >> >> Kill the NULL check - it is a silly coding error.
> > >> >> An OOPS is just as easy to debug.
> > >> >>
> > >> >
> > >> >
> > >> > I don't think that one single driver should kill the whole system. It's
> > >> > 100% an error, but kernel can recover from it (for example disconnect
> > >> > the driver, since it's broken).
> > >> >
> > >> >
> > >> > AFIAK, Greg and Linus do not like BUG_ONs in recoverable state...
> > >> > Correct me, if I am wrong
> > >> >
> > >> Oops, I thought about BUG_ON() instead of WARN_ON(), sorry for
> > >> confusion. My point is "we should not let the box boom".
> > >
> > >
> > > There is no point checking for NULL that just can't happen.
> > > In this case all the callers will pass the address of a local.
> > > There really is no point checking.
> > >
> >
> > We not always read in local variable, there are few places, where we
> > read into passed buffer.
>
> It is still a very local coding bug.
>
> 	David

Sure, but is defensive programming so bad?


Greg, what your opinion about this NULL check?




With regards,
Pavel Skripkin