linux-kernel - Re: [PATCH] fanotify: correct broken ref counting in case adding a mark failed

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Date:	Tue, 09 Nov 2010 15:21:11 -0500
From:	Eric Paris <eparis@...hat.com>
To:	Lino Sanfilippo <LinoSanfilippo@....de>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] fanotify: correct broken ref counting in case adding a
 mark failed

On Tue, 2010-11-09 at 18:18 +0100, Lino Sanfilippo wrote:
> If adding a mount or inode mark failed fanotify_free_mark() is called explicitly.
>     But at this time the mark has already been put into the destroy list of the
>     fsnotify_mark kernel thread. If the thread is too slow it will try to decrease
>     the reference of a mark, that has already been freed by fanotify_free_mark().
>     (If its fast enough it will only decrease the marks ref counter from 2 to 1 - note
>     that the counter has been increased to 2 in add_mark() - which has practically no
>     effect.)
>     This patch fixes the ref counting by not calling free_mark() explicitly, but
>     decreasing the ref counter and rely on the fsnotify_mark thread to cleanup in
>     case adding the mark has failed.
> 
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>

applied to http://git.infradead.org/users/eparis/notify.git/ #for-next

-Eric

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