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

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Message-ID: <4DB023C7.5070007@siemens.com>
Date:	Thu, 21 Apr 2011 14:32:07 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Chris Wright <chrisw@...s-sol.org>,
	David Woodhouse <David.Woodhouse@...el.com>
CC:	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: [PATCH v2] intel-iommu: Fix use after release during device attach

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>
---
 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--;
 	}
-- 
1.7.1
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