linux-kernel - Re: [PATCH 03/15] kmemleak: Add the slab memory allocation/freeing hooks

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Message-Id: <1229619764.16418.54.camel@pc1117.cambridge.arm.com>
Date:	Thu, 18 Dec 2008 17:02:44 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/15] kmemleak: Add the slab memory allocation/freeing
	hooks

On Thu, 2008-12-18 at 10:49 -0600, Christoph Lameter wrote:
> On Thu, 18 Dec 2008, Catalin Marinas wrote:
> 
> > In the ____cache_alloc() kmemleak clears the
> > cachep->array->entry[ac->avail] pointer but this may not be enough as
> > freed and later re-allocated objects may have pointers in the alien
> > cache (is that correct?). A better approach (haven't tried it yet) would
> > be not to scan objects allocated via alloc_arraycache() at all. However,
> > there is still the initarray_cache/generic which are automatically
> > scanned via the data section (unless I add an attribute to place them in
> > a different, not scanned, section).
> 
> An allocated object is not part of any cache in SLAB. Only freed objects
> are kept in the slab queues. A freed object can only be in one queue at a
> time.

OK, but is there a chance that an stale pointer remains in such caches?
There seems to be the transfer_objects() function that moves pointers
around but doesn't clear the source values.

-- 
Catalin

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