RE: [PATCH v5 09/15] iommu/vt-d: Check ownership for PASIDs from user-space

["Liu, Yi L" <yi.l.liu@intel.com>]

Hi Eric,

> From: Auger Eric <eric.auger@redhat.com>
> Sent: Monday, July 20, 2020 12:06 AM
> 
> Hi Yi,
> 
> On 7/12/20 1:21 PM, Liu Yi L wrote:
> > When an IOMMU domain with nesting attribute is used for guest SVA, a
> > system-wide PASID is allocated for binding with the device and the domain.
> > For security reason, we need to check the PASID passsed from user-space.
> passed

got it.

> > e.g. page table bind/unbind and PASID related cache invalidation.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Eric Auger <eric.auger@redhat.com>
> > Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Cc: Joerg Roedel <joro@8bytes.org>
> > Cc: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >  drivers/iommu/intel/iommu.c | 10 ++++++++++
> >  drivers/iommu/intel/svm.c   |  7 +++++--
> >  2 files changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 4d54198..a9504cb 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -5436,6 +5436,7 @@ intel_iommu_sva_invalidate(struct iommu_domain
> *domain, struct device *dev,
> >  		int granu = 0;
> >  		u64 pasid = 0;
> >  		u64 addr = 0;
> > +		void *pdata;
> >
> >  		granu = to_vtd_granularity(cache_type, inv_info->granularity);
> >  		if (granu == -EINVAL) {
> > @@ -5456,6 +5457,15 @@ intel_iommu_sva_invalidate(struct iommu_domain
> *domain, struct device *dev,
> >  			 (inv_info->granu.addr_info.flags &
> IOMMU_INV_ADDR_FLAGS_PASID))
> >  			pasid = inv_info->granu.addr_info.pasid;
> >
> > +		pdata = ioasid_find(dmar_domain->ioasid_sid, pasid, NULL);
> > +		if (!pdata) {
> > +			ret = -EINVAL;
> > +			goto out_unlock;
> > +		} else if (IS_ERR(pdata)) {
> > +			ret = PTR_ERR(pdata);
> > +			goto out_unlock;
> > +		}
> > +
> >  		switch (BIT(cache_type)) {
> >  		case IOMMU_CACHE_INV_TYPE_IOTLB:
> >  			/* HW will ignore LSB bits based on address mask */
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index d2c0e1a..212dee0 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -319,7 +319,7 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain,
> struct device *dev,
> >  	dmar_domain = to_dmar_domain(domain);
> >
> >  	mutex_lock(&pasid_mutex);
> > -	svm = ioasid_find(INVALID_IOASID_SET, data->hpasid, NULL);
> I do not get what the call was supposed to do before that patch?

you mean patch 10/15 by "that patch", right? the ownership check should
be done as to prevent illegal bind request from userspace. before patch
10/15, it should be added.

> > +	svm = ioasid_find(dmar_domain->ioasid_sid, data->hpasid, NULL);
> >  	if (IS_ERR(svm)) {
> >  		ret = PTR_ERR(svm);
> >  		goto out;
> > @@ -436,6 +436,7 @@ int intel_svm_unbind_gpasid(struct iommu_domain
> *domain,
> >  			    struct device *dev, ioasid_t pasid)
> >  {
> >  	struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> > +	struct dmar_domain *dmar_domain;
> >  	struct intel_svm_dev *sdev;
> >  	struct intel_svm *svm;
> >  	int ret = -EINVAL;
> > @@ -443,8 +444,10 @@ int intel_svm_unbind_gpasid(struct iommu_domain
> *domain,
> >  	if (WARN_ON(!iommu))
> >  		return -EINVAL;
> >
> > +	dmar_domain = to_dmar_domain(domain);
> > +
> >  	mutex_lock(&pasid_mutex);
> > -	svm = ioasid_find(INVALID_IOASID_SET, pasid, NULL);
> > +	svm = ioasid_find(dmar_domain->ioasid_sid, pasid, NULL);
> just to make sure, about the locking, can't domain->ioasid_sid change
> under the hood?

I guess not. intel_svm_unbind_gpasid() and iommu_domain_set_attr()
is called by vfio today, and within vfio, there is vfio_iommu->lock.

Regards,
Yi Liu

> 
> Thanks
> 
> Eric
> >  	if (!svm) {
> >  		ret = -EINVAL;
> >  		goto out;
> >