linux-ext4 - Re: 2.6.32-rc6 BUG at mm/slab.c:2869!

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Message-ID: <20090821123657.GA27001@hash.localnet>
Date:	Fri, 21 Aug 2009 08:36:57 -0400
From:	Bob Copeland <me@...copeland.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	Eric Paris <eparis@...hat.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org
Subject: Re: 2.6.32-rc6 BUG at mm/slab.c:2869!

On Fri, Aug 21, 2009 at 08:46:37AM +0200, Vegard Nossum wrote:
> 2009/8/21 Bob Copeland <me@...copeland.com>:
> > WARNING: kmemcheck: Caught 32-bit read from freed memory (f34a443c)
> > eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee008a06f700011000
> >  a a a a a a a a a a a a a a a a a a a a a a a a f f f f f f f f
> >
> > I think that is list_empty() here where %eax is list_head
> > and event_list->next is the read location... which definitely
> > doesn't look like a pointer, if I'm reading it correctly.
> 
> I think f34a443c is a valid pointer. On my machine, at least:

I meant list->next, which was 00100100 here.  (By the way, my first
time using kmemcheck, very nice tool!)

[race condition explanation snipped]

> I think that's it. Any thoughts? I put Eric Paris on Cc.

Thanks!  With a fresh pull containing the fsnotify fix the kmemcheck
warning is gone.  So unless I see anything else I'll assume that this
one is already fixed, sorry for the false alarm.

-- 
Bob Copeland %% www.bobcopeland.com

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