linux-kernel - Re: [PATCH v2] intel-iommu: Fix use after release during device attach

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Date:	Thu, 21 Apr 2011 07:02:16 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	David Woodhouse <dwmw2@...radead.org>,
	iommu@...ts.linux-foundation.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>, Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH v2] intel-iommu: Fix use after release during device
 attach

* Jan Kiszka (jan.kiszka@...mens.com) wrote:
> On 2011-01-04 11:42, Jan Kiszka wrote:
> > Am 10.12.2010 19:44, Chris Wright wrote:
> >> * Jan Kiszka (jan.kiszka@...mens.com) wrote:
> >>>>>> --- a/drivers/pci/intel-iommu.c
> >>>>>> +++ b/drivers/pci/intel-iommu.c
> >>>>>> @@ -3627,9 +3627,9 @@ static int intel_iommu_attach_device(struct
> >>>>>> iommu_domain *domain,
> >>>>>>
> >>>>>>  		pte = dmar_domain->pgd;
> >>>>>>  		if (dma_pte_present(pte)) {
> >>>>>> -			free_pgtable_page(dmar_domain->pgd);
> >>>>>>  			dmar_domain->pgd = (struct dma_pte *)
> >>>>>>  				phys_to_virt(dma_pte_addr(pte));
> >>
> >> While here, might as well remove the unnecessary cast.
> >>
> >>>>>> +			free_pgtable_page(pte);
> >>>>>>  		}
> >>>>>>  		dmar_domain->agaw--;
> >>>>>>  	}
> >>>>>
> >>>>> Reviewed-by: Sheng Yang <sheng@...ux.intel.com>
> >>
> >> Acked-by: Chris Wright <chrisw@...s-sol.org>
> >>
> >>>>> CC iommu mailing list and David.
> >>>>
> >>>> Ping...
> >>>>
> >>>> I think this fix also qualifies for stable (.35 and .36).
> >>>>
> >>>
> >>> Still not merged?
> >>
> >> David, do you plan to pick this one up?
> >>
> >> thanks,
> >> -chris
> > 
> > Hmm, still no reaction. Trying David's Intel address now...
> > 
> > Jan
> > 
> 
> Walking through my old queues, I came across this one again.
> 
> Given the still lacking reaction from the official maintainer, I'm a
> bit confused about the state of intel-iommu. Is it unmaintained? Should
> this bug fix better be routed through the KVM tree as its only in-tree
> user? Please enlighten me.
> 
> Note that the patch became stable material for 35..38 in the meantime,
> and it should go into 39 before release as well.
> 
> Thanks,
> Jan
> 
> -------8<--------
> 
> Obtain the new pgd pointer before releasing the page containing this
> value. Remove unneeded cast at this chance as well.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>

Acked-by: Chris Wright <chrisw@...s-sol.org>

> ---
>  drivers/pci/intel-iommu.c |    5 ++---
>  1 files changed, 2 insertions(+), 3 deletions(-)
> 
> v1->v2: Clean up cast as suggested by Chris.
> 
> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> index 505c1c7..b3e5c43 100644
> --- a/drivers/pci/intel-iommu.c
> +++ b/drivers/pci/intel-iommu.c
> @@ -3607,9 +3607,8 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
>  
>  		pte = dmar_domain->pgd;
>  		if (dma_pte_present(pte)) {
> -			free_pgtable_page(dmar_domain->pgd);
> -			dmar_domain->pgd = (struct dma_pte *)
> -				phys_to_virt(dma_pte_addr(pte));
> +			dmar_domain->pgd = phys_to_virt(dma_pte_addr(pte));
> +			free_pgtable_page(pte);
>  		}
>  		dmar_domain->agaw--;
>  	}
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