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

[Pavel Skripkin]

On 8/27/21 10:12 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> On Thu, Aug 26, 2021 at 11:03:04PM +0300, Pavel Skripkin wrote:
> > 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?
>
> Yes it is, for when it is not needed.
>
> > Greg, what your opinion about this NULL check?
>
> Never check for things that you know are not going to happen.  Otherwise
> the kernel would just be full of pointless checks everywhere.
>
> And why are you waiting for me to tell you this?  Why do you not believe
> David?


Just wanted to hear more opinions on this check. I believe David, but 
opinions of other people are important too, IMO




With regards,
Pavel Skripkin