linux-kernel - Re: Slab corruption in fanotify_free

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Message-ID: <alpine.DEB.2.02.1401221347390.22014@chino.kir.corp.google.com>
Date:	Wed, 22 Jan 2014 13:49:26 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Jiri Kosina <jkosina@...e.cz>
cc:	Jan Kara <jack@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Eric Paris <eparis@...isplace.org>,
	Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org
Subject: Re: Slab corruption in fanotify_free_event()

On Wed, 22 Jan 2014, Jiri Kosina wrote:

> Hi,
> 
> booting current Linus' tree (df32e43a), I am getting
> 
>  Slab corruption (Not tainted): fanotify_event_info start=ffff8800372e3320, len=64
>  Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
>  Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
>  030: 6b 6b 6b 6b 6b 6b 6b 6b 00 00 00 00 6b 6b 6b a5  kkkkkkkk....kkk.
>  Prev obj: start=ffff8800372e32c8, len=64
>  Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
>  Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
>  000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>  010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>  Next obj: start=ffff8800372e3378, len=64
>  Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
>  Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
>  000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
>  010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
> 
> I guess this is due to
> 
> 	commit 7053aee26a3548ebaba046ae2e52396ccf56ac6c
> 	Author: Jan Kara <jack@...e.cz>
> 	Date:   Tue Jan 21 15:48:14 2014 -0800
> 
> 	    fsnotify: do not share events between notification groups
> 
> as I am not able to see any other recent changes in that area. Haven't 
> been looking at the patch closely enough to debug this yet ... sending 
> this as an early heads-up.
> 

Dave Jones reports slab poison values getting overwritten and bisected it 
to the same commit.  The discussion is at 
http://marc.info/?t=139037220800006.
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