Re: [PATCH] rtc: fix kernel panic on second use of SIGIO nofitication

[David Brownell <david-b@pacbell.net>]

On Thursday 02 October 2008, Alessandro Zummo wrote:
> On Thu, 2 Oct 2008 14:49:41 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Sun, 14 Sep 2008 20:11:27 +0200
> > Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> > 
> > > When user space uses SIGIO notification and forgets to disable it before
> > > closing file descriptor, rtc->async_queue contains stale pointer to struct
> > > file. When user space enables again SIGIO notification in different process,
> > > kernel dereferences this (poisoned) pointer and crashes.
> > > 
> > > So disable SIGIO notification on close.
> > > 
> > 
> > David, Alessandro: can we please have a review-n-ack of this one for
> > 2.6.27 and earlier?  
> > 
> > Thanks.
> > 
> > From: Marcin Slusarz <marcin.slusarz@gmail.com>
> > 
> > When userspace uses SIGIO notification and forgets to disable it before
> > closing file descriptor, rtc->async_queue contains stale pointer to struct
> > file.  When user space enables again SIGIO notification in different
> > process, kernel dereferences this (poisoned) pointer and crashes.
> > 
> > So disable SIGIO notification on close.
> 
>  [...]
> > 
> > Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
> > Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
> > Cc: David Brownell <dbrownell@users.sourceforge.net>
> > Cc: <stable@kernel.org>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> 
>  
>  Acked-by: Alessandro Zummo <a.zummo@towertech.it>

Acked-by: David Brownell <dbrownell@users.sourceforge.net>

Seemed "obviously good" anti-oops medicine to me, then I double
checked against some code that is AFAIK still correct..