Messages in this thread | | | Date | Thu, 11 Jun 2020 16:58:35 -0700 | From | Jacob Pan <> | Subject | Re: [PATCH v2 3/3] iommu/vt-d: Sanity check uapi argsz filled by users |
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On Thu, 11 Jun 2020 14:55:18 -0600 Alex Williamson <alex.williamson@redhat.com> wrote:
> On Thu, 11 Jun 2020 13:02:24 -0700 > Jacob Pan <jacob.jun.pan@linux.intel.com> wrote: > > > On Thu, 11 Jun 2020 11:08:16 -0600 > > Alex Williamson <alex.williamson@redhat.com> wrote: > > > > > On Wed, 10 Jun 2020 21:12:15 -0700 > > > Jacob Pan <jacob.jun.pan@linux.intel.com> wrote: > > > > > > > IOMMU UAPI data has an argsz field which is filled by user. As > > > > the data structures expands, argsz may change. As the UAPI data > > > > are shared among different architectures, extensions of UAPI > > > > data could be a result of one architecture which has no impact > > > > on another. Therefore, these argsz santity checks are performed > > > > in the model specific IOMMU drivers. This patch adds sanity > > > > checks in the VT-d to ensure argsz passed by userspace matches > > > > feature flags and other contents. > > > > > > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > > > > --- > > > > drivers/iommu/intel-iommu.c | 16 ++++++++++++++++ > > > > drivers/iommu/intel-svm.c | 12 ++++++++++++ > > > > 2 files changed, 28 insertions(+) > > > > > > > > diff --git a/drivers/iommu/intel-iommu.c > > > > b/drivers/iommu/intel-iommu.c index 27ebf4b9faef..c98b5109684b > > > > 100644 --- a/drivers/iommu/intel-iommu.c > > > > +++ b/drivers/iommu/intel-iommu.c > > > > @@ -5365,6 +5365,7 @@ intel_iommu_sva_invalidate(struct > > > > iommu_domain *domain, struct device *dev, struct > > > > device_domain_info *info; struct intel_iommu *iommu; > > > > unsigned long flags; > > > > + unsigned long minsz; > > > > int cache_type; > > > > u8 bus, devfn; > > > > u16 did, sid; > > > > @@ -5385,6 +5386,21 @@ intel_iommu_sva_invalidate(struct > > > > iommu_domain *domain, struct device *dev, if > > > > (!(dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE)) return > > > > -EINVAL; > > > > + minsz = offsetofend(struct iommu_cache_invalidate_info, > > > > padding); > > > > > > Would it still be better to look for the end of the last field > > > that's actually used to avoid the code churn and oversights > > > if/when the padding field does get used and renamed? > > > > > My thought was that if the padding gets partially re-purposed, the > > remaining padding would still be valid for minsz check. The > > extension rule ensures that there is no size change other the > > variable size union at the end. So use padding would avoid the > > churn, or i am totally wrong? > > No, it's trying to predict the future either way. I figured checking > minsz against the fields we actually consume allows complete use of > the padding fields and provides a little leniency to the user. We'd > need to be careful though that if those fields are later used by this > driver, the code would still need to accept the smaller size. If the > union was named rather than anonymous we could just use offsetof() to > avoid directly referencing the padding fields. > I will change it to named union.
Thanks,
> > > Per my comment on patch 1/, this also seems like where the device > > > specific IOMMU driver should also have the responsibility of > > > receiving a __user pointer to do the copy_from_user() here. vfio > > > can't know which flags require which fields to make a UAPI with > > > acceptable compatibility guarantees otherwise. > > > > > Right, VFIO cannot do compatibility guarantees, it is just seem to > > be that VFIO has enough information to copy_from_user sanely & > > safely and handle over to IOMMU. Please help define the > > roles/responsibilities in my other email. Then I will follow the > > guideline. > > We can keep that part of the discussion in the other thread. Thanks, > > Alex > > > > > + if (inv_info->argsz < minsz) > > > > + return -EINVAL; > > > > + > > > > + /* Sanity check user filled invalidation dat sizes */ > > > > + if (inv_info->granularity == IOMMU_INV_GRANU_ADDR && > > > > + inv_info->argsz != offsetofend(struct > > > > iommu_cache_invalidate_info, > > > > + addr_info)) > > > > + return -EINVAL; > > > > + > > > > + if (inv_info->granularity == IOMMU_INV_GRANU_PASID && > > > > + inv_info->argsz != offsetofend(struct > > > > iommu_cache_invalidate_info, > > > > + pasid_info)) > > > > + return -EINVAL; > > > > + > > > > spin_lock_irqsave(&device_domain_lock, flags); > > > > spin_lock(&iommu->lock); > > > > info = get_domain_info(dev); > > > > diff --git a/drivers/iommu/intel-svm.c > > > > b/drivers/iommu/intel-svm.c index 35b43fe819ed..64dc2c66dfff > > > > 100644 --- a/drivers/iommu/intel-svm.c > > > > +++ b/drivers/iommu/intel-svm.c > > > > @@ -235,15 +235,27 @@ int intel_svm_bind_gpasid(struct > > > > iommu_domain *domain, struct device *dev, struct dmar_domain > > > > *dmar_domain; struct intel_svm_dev *sdev; > > > > struct intel_svm *svm; > > > > + unsigned long minsz; > > > > int ret = 0; > > > > > > > > if (WARN_ON(!iommu) || !data) > > > > return -EINVAL; > > > > > > > > + /* > > > > + * We mandate that no size change in IOMMU UAPI data > > > > before the > > > > + * variable size union at the end. > > > > + */ > > > > + minsz = offsetofend(struct iommu_gpasid_bind_data, > > > > padding); > > > > > > Same. Thanks, > > > > > > Alex > > > > > > > + if (data->argsz < minsz) > > > > + return -EINVAL; > > > > + > > > > if (data->version != IOMMU_GPASID_BIND_VERSION_1 || > > > > data->format != IOMMU_PASID_FORMAT_INTEL_VTD) > > > > return -EINVAL; > > > > > > > > + if (data->argsz != offsetofend(struct > > > > iommu_gpasid_bind_data, vtd)) > > > > + return -EINVAL; > > > > + > > > > if (!dev_is_pci(dev)) > > > > return -ENOTSUPP; > > > > > > > > > > > [Jacob Pan] > > >
[Jacob Pan]
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