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

Chris Wright
2011-04-21T14:03:18Z

* Jan Kiszka (jan.kiszka@siemens.com) wrote:
> On 2011-01-04 11:42, Jan Kiszka wrote:
> > Am 10.12.2010 19:44, Chris Wright wrote:
> >> * Jan Kiszka (jan.kiszka@siemens.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@linux.intel.com>
> >>
> >> Acked-by: Chris Wright <chrisw@sous-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@siemens.com>

Acked-by: Chris Wright <chrisw@sous-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--;
> }