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

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Date:	Thu, 2 Oct 2008 16:44:51 -0700
From:	David Brownell <david-b@...bell.net>
To:	Alessandro Zummo <alessandro.zummo@...ertech.it>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Marcin Slusarz <marcin.slusarz@...il.com>,
	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	stable@...nel.org
Subject: Re: [PATCH] rtc: fix kernel panic on second use of SIGIO nofitication

On Thursday 02 October 2008, Alessandro Zummo wrote:
> On Thu, 2 Oct 2008 14:49:41 -0700
> Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > On Sun, 14 Sep 2008 20:11:27 +0200
> > Marcin Slusarz <marcin.slusarz@...il.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@...il.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@...il.com>
> > Cc: Alessandro Zummo <alessandro.zummo@...ertech.it>
> > Cc: David Brownell <dbrownell@...rs.sourceforge.net>
> > Cc: <stable@...nel.org>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> 
>  
>  Acked-by: Alessandro Zummo <a.zummo@...ertech.it>

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

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