linux-kernel - Re: [PATCH 5/5] staging/otus: Move a dereference below a NULL test

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Message-ID: <Pine.LNX.4.64.0907111331170.31089@ask.diku.dk>
Date:	Sat, 11 Jul 2009 13:32:13 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>, gregkh@...e.de,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 5/5] staging/otus: Move a dereference below a NULL test

On Sat, 11 Jul 2009, Jiri Slaby wrote:

> On 07/11/2009 12:17 PM, Jaswinder Singh Rajput wrote:
> > On Sat, 2009-07-11 at 10:17 +0200, Jiri Slaby wrote:
> >> On 07/11/2009 09:51 AM, Julia Lawall wrote:
> >>> --- a/drivers/staging/otus/wwrap.c
> >>> +++ b/drivers/staging/otus/wwrap.c
> >>> @@ -1016,12 +1016,13 @@ void kevent(struct work_struct *work)
> >>>  {
> >>>      struct usbdrv_private *macp =
> >>>                 container_of(work, struct usbdrv_private, kevent);
> >>> -    zdev_t *dev = macp->device;
> >>> +    zdev_t *dev;
> >>>  
> >>>      if (macp == NULL)
> >>>      {
> >>>          return;
> >>>      }
> >>
> >> The test is rather useless here.
> >>
> > 
> > Why useless, it should be non-null before setting to dev.
> 
> Even if work was NULL, macp won't be NULL.

work could be a small negative number such that calling container_of would 
return 0.

julia
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