Re: [PATCH] b43: Fix smatch warning

["Michael Büsch" <m@bues.ch>]

On Sat, 27 Aug 2011 14:15:59 -0500
Larry Finger <Larry.Finger@lwfinger.net> wrote:

> On 08/27/2011 01:54 PM, Michael Büsch wrote:
> > On Sat, 27 Aug 2011 13:26:00 -0500
> > Larry Finger<Larry.Finger@lwfinger.net>  wrote:
> >
> >>    CHECK   drivers/net/wireless/b43/main.c
> >> drivers/net/wireless/b43/main.c +4115 b43_wireless_core_stop(7) warn: variable dereferenced before check 'dev'
> >
> >> This is next material.
> >
> > -next, just because the bug is not in the current kernel?
> > Or because you think this is harmless?
> >
> > I'm not sure whether this is harmless. It effectively is that kind
> > of bug that triggers dangerous compiler optimizations.
> > I think the compiler has some freedom to assume dev can not be NULL when
> > the function is entered and thus optimize out the !dev check.
> 
> No, the check has to be left in due to the changing of dev in the routine 
> followed by a 'goto redo'.

I think the compiler is still free to emit the !dev check twice.
Or the other way around: Emit it correctly for the "goto" case and
don't emit it for the function-enter case (and directly check dev->status).

> In fact, a bug in the original code is unlikely, but my patch did add one. I 
> think the code should be
> 
> 	if (!dev)
> 		return NULL;
> 	wl = dev->wl;
> redo:

yes


-- 
Greetings, Michael.