linux-kernel - Re: [PATCH] 3c507.c: remove unused NULL pointer check

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Date:	Mon, 21 Dec 2009 12:31:11 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	Alexander Strakh <strakh@...ras.ru>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Donald Becker <becker@...ld.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] 3c507.c: remove unused NULL pointer check

On Mon, 21 Dec 2009 17:56:39 +0100
Oliver Hartkopp <socketcan@...tkopp.net> wrote:

> Alexander Strakh wrote:
> > 	In driver drivers/net/3c507.c in function Iirqreturn_t el16_interrupt:
> > 1. If in line 555 dev = NULL then we goto line 556
> > 2. In line 556 we have null dereference because pr_err called with dev->name 
> > in third parameter.
> >  555        if (dev == NULL) {
> >  556                pr_err("%s: net_interrupt(): irq %d for unknown device.
> > \n",
> >  557                        dev->name, irq);
> >  558                return IRQ_NONE;
> >  559        }
> > 
> > Found by Linux Device Drivers Verification (Svace detector)
> > 
> > Remove unused NULL pointer check.
> 
> You are obviously doing more than that ...
> 
> > 
> > Signed-off-by: Alexander Strakh <strakh@...ras.ru>
> > 
> > ---
> > diff --git a/./0000/drivers/net/3c507.c b/./moder/drivers/net/3c507.c
> > index fbc2311..3bfb3dd 100644
> > --- a/./0000/drivers/net/3c507.c
> > +++ b/./moder/drivers/net/3c507.c
> > @@ -552,12 +552,6 @@ static irqreturn_t el16_interrupt(int irq, void *dev_id)
> >  	ushort ack_cmd = 0;
> >  	void __iomem *shmem;
> >  
> > -	if (dev == NULL) {
> > -		pr_err("%s: net_interrupt(): irq %d for unknown device.\n",
> > -			dev->name, irq);
> 
> You are changing real funcionality here!
> 
> If you want to fix it, fix the pr_err() but do not remove the "return
> IRQ_NONE" entirely.
> 
> This looks like an introduction of a bug.
> 
> Regards,
> Oliver
> 
> 
> > -		return IRQ_NONE;
> > -	}
> > -

Interrupts will never be called with third parameter of NULL. It is really
bogus impossible to reach code.

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