linux-kernel - Re: [PATCH] mm: dmapool: fix possible use after free in dmam_pool

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Message-ID: <20110609102038.GE11773@htj.dyndns.org>
Date:	Thu, 9 Jun 2011 12:20:38 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Maxin B John <maxin.john@...il.com>
Cc:	eike-kernel@...tec.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	dima@...roid.com, willy@...ux.intel.com, segooon@...il.com,
	jkosina@...e.cz, tglx@...utronix.de
Subject: Re: [PATCH] mm: dmapool: fix possible use after free in
 dmam_pool_destroy()

Hello,

On Thu, Jun 02, 2011 at 05:22:42PM +0300, Maxin B John wrote:
> > The pool itself is not used there, only the address where the pool
> > has been.This will only lead to any trouble if something else is allocated to
> > the same place and inserted into the devres list of the same device between
> > the dma_pool_destroy() and devres_destroy().

Which can't happen.  devres release is bound to device driver model
and a device can't be re-attached before release is complete.
ie. those operations are serialized, so the failure mode is only
theoretical.

> Thank you very much for explaining it in detail. 
> 
> > But I agree that this is bad style. But if you are going to change
> > this please also have a look at devm_iounmap() in lib/devres.c. Maybe also the
> > devm_*irq* functions need the same changes.
> 
> As per your suggestion, I have made similar modifications for lib/devres.c and
> kernel/irq/devres.c
> 
> CCed the maintainers of the respective files.
>  
> Signed-off-by: Maxin B. John <maxin.john@...il.com>

But it shouldn't hurt and if it helps memleak.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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