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

Jan Kiszka
2010-11-02T07:46:22Z

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Am 02.11.2010 08:31, Sheng Yang wrote:
> On Tuesday 02 November 2010 15:05:51 Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> Obtail the new pgd pointer before releasing the page containing this
>> value.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>
>> Who is taking care of this? The kvm tree?
>>
>> drivers/pci/intel-iommu.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
>> index 4789f8e..35463dd 100644
>> --- 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));
>> + free_pgtable_page(pte);
>> }
>> dmar_domain->agaw--;
>> }
>
> Reviewed-by: Sheng Yang <sheng@linux.intel.com>
>
> CC iommu mailing list and David.
>
> OK, Jan, I got your meaning now. And it's not the exactly swap. :)
>
> I think the old code is safe, seems it's broken(exposed) by:
>
> commit 1a8bd481bfba30515b54368d90a915db3faf302f
> Author: David Woodhouse <David.Woodhouse@intel.com>
> Date: Tue Aug 10 01:38:53 2010 +0100
>
> intel-iommu: Fix 32-bit build warning with __cmpxchg()
>
> drivers/pci/intel-iommu.c: In function 'dma_pte_addr':
> drivers/pci/intel-iommu.c:239: warning: passing argument 1 of '__cmpxchg64'
> from incompatible pointer typ
>
> It seems that __cmpxchg64() now cares about the type of its pointer argument,
> so give it a (uint64_t *) instead of a pointer to a structure which contains
> only that.
>
> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
>
> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> index c9171be..603cdc0 100644
> --- a/drivers/pci/intel-iommu.c
> +++ b/drivers/pci/intel-iommu.c
> @@ -236,7 +236,7 @@ static inline u64 dma_pte_addr(struct dma_pte *pte)
> return pte->val & VTD_PAGE_MASK;
> #else
> /* Must have a full atomic 64-bit read */
> - return __cmpxchg64(pte, 0ULL, 0ULL) & VTD_PAGE_MASK;
> + return __cmpxchg64(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;
> #endif
> }
>
> Seems here is the only affected code?

CONFIG_64BIT is on here, so this change did not make a difference for me.

Jan

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