linux-kernel - Re: [PATCH] kvm: fix coalesced

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Message-ID: <20090527203540.GJ20823@sequoia.sous-sol.org>
Date:	Wed, 27 May 2009 13:35:40 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Gregory Haskins <gregory.haskins@...il.com>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Gregory Haskins <ghaskins@...ell.com>, avi@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kvm: fix coalesced_mmio leak on shutdown

* Gregory Haskins (gregory.haskins@...il.com) wrote:
> Chris Wright wrote:
> > * Gregory Haskins (ghaskins@...ell.com) wrote:
> >> It would appear that we are invoking kfree() on the wrong pointer in the
> >> destructor for the coalesced_mmio device.  This would result in a potential
> >> leak during shutdown.
> >
> > Happens to work and not leak:
> >
> > struct kvm_coalesced_mmio_dev { 
> >         struct kvm_io_device dev;
> >         struct kvm *kvm;
> >         int nb_zones;
> >         struct kvm_coalesced_mmio_zone zone[KVM_COALESCED_MMIO_ZONE_MAX];
> > };
> >
> >   
> Ah, yes.  That explains it.  Still sloppy, tho.

Definitely.

> >>  static void coalesced_mmio_destructor(struct kvm_io_device *this)
> >>  {
> >> -	kfree(this);
> >> +	struct kvm_coalesced_mmio_dev *dev =
> >> +		(struct kvm_coalesced_mmio_dev *)this->private;
> >>     
> >
> > I think container_of() makes more sense here.
> 
> I was working on that patch when I noticed the "leak" above.  Figured I
> should send the fix out first, in case my container_of patch is shot down.
> 
> Just polishing it up now.  Will send out soon.

Sounds good.

thanks,
-chris
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