Re: [PATCH v3 4/5] iommu/uapi: Handle data and argsz filled by users

[Jacob Pan]

On Wed, 24 Jun 2020 14:54:49 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> Hi Jacob,
> 
> On 2020/6/24 1:03, Jacob Pan wrote:
> > IOMMU UAPI data has a user filled argsz field which indicates the
> > data length comes with the API call. User data is not trusted,
> > argsz must be validated based on the current kernel data size,
> > mandatory data size, and feature flags.
> > 
> > User data may also be extended, results in possible argsz increase.
> > Backward compatibility is ensured based on size and flags checking.
> > Details are documented in Documentation/userspace-api/iommu.rst
> > 
> > This patch adds sanity checks in both IOMMU layer and vendor code,
> > where VT-d is the only user for now.
> > 
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/intel/svm.c |  3 ++
> >   drivers/iommu/iommu.c     | 96
> > ++++++++++++++++++++++++++++++++++++++++++++---
> > include/linux/iommu.h     |  7 ++-- 3 files changed, 98
> > insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index 713b3a218483..237db56878c0 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -244,6 +244,9 @@ int intel_svm_bind_gpasid(struct iommu_domain
> > *domain, struct device *dev, data->format !=
> > IOMMU_PASID_FORMAT_INTEL_VTD) return -EINVAL;
> >   
> > +	if (data->argsz != offsetofend(struct
> > iommu_gpasid_bind_data, vendor.vtd))
> > +		return -EINVAL;  
> 
> Need to do size check in intel_iommu_sva_invalidate() as well?
> 
No need. The difference is that there is no
vendor specific union for intel_iommu_sva_invalidate().

Generic flags are used to process invalidation data inside
intel_iommu_sva_invalidate().
> > +
> >   	if (!dev_is_pci(dev))
> >   		return -ENOTSUPP;
> >   
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index d43120eb1dc5..4a025c429b41 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -1951,22 +1951,108 @@ int iommu_attach_device(struct
> > iommu_domain *domain, struct device *dev)
> > EXPORT_SYMBOL_GPL(iommu_attach_device); 
> >   int iommu_cache_invalidate(struct iommu_domain *domain, struct
> > device *dev,
> > -			   struct iommu_cache_invalidate_info
> > *inv_info)
> > +			void __user *uinfo)  
> 
> Nit: keep it aligned.
> 
> >   {
> > +	struct iommu_cache_invalidate_info inv_info;
> > +	unsigned long minsz, maxsz;
> > +
> >   	if (unlikely(!domain->ops->cache_invalidate))
> >   		return -ENODEV;
> >   
> > -	return domain->ops->cache_invalidate(domain, dev,
> > inv_info);
> > +	/* Current kernel data size is the max to be copied from
> > user */
> > +	maxsz = sizeof(struct iommu_cache_invalidate_info);
> > +	memset((void *)&inv_info, 0, maxsz);
> > +
> > +	/*
> > +	 * No new spaces can be added before the variable sized
> > union, the
> > +	 * minimum size is the offset to the union.
> > +	 */
> > +	minsz = offsetof(struct iommu_cache_invalidate_info,
> > granu); +
> > +	/* Copy minsz from user to get flags and argsz */
> > +	if (copy_from_user(&inv_info, uinfo, minsz))
> > +		return -EFAULT;
> > +
> > +	/* Fields before variable size union is mandatory */
> > +	if (inv_info.argsz < minsz)
> > +		return -EINVAL;
> > +	/*
> > +	 * User might be using a newer UAPI header, we shall let
> > IOMMU vendor
> > +	 * driver decide on what size it needs. Since the UAPI
> > data extension
> > +	 * can be vendor specific, larger argsz could be the
> > result of extension
> > +	 * for one vendor but it should not affect another vendor.
> > +	 */
> > +	/*
> > +	 * User might be using a newer UAPI header which has a
> > larger data
> > +	 * size, we shall support the existing flags within the
> > current
> > +	 * size.
> > +	 */
> > +	if (inv_info.argsz > maxsz)
> > +		inv_info.argsz = maxsz;
> > +
> > +	/* Checking the exact argsz based on generic flags */
> > +	if (inv_info.granularity == IOMMU_INV_GRANU_ADDR &&
> > +		inv_info.argsz != offsetofend(struct
> > iommu_cache_invalidate_info,
> > +					granu.addr_info))
> > +		return -EINVAL;
> > +
> > +	if (inv_info.granularity == IOMMU_INV_GRANU_PASID &&
> > +		inv_info.argsz != offsetofend(struct
> > iommu_cache_invalidate_info,
> > +					granu.pasid_info))
> > +		return -EINVAL;
> > +
> > +	/* Copy the remaining user data _after_ minsz */
> > +	if (copy_from_user((void *)&inv_info + minsz, uinfo +
> > minsz,
> > +				inv_info.argsz - minsz))
> > +		return -EFAULT;
> > +
> > +	return domain->ops->cache_invalidate(domain, dev,
> > &inv_info); }
> >   EXPORT_SYMBOL_GPL(iommu_cache_invalidate);
> >   
> > -int iommu_sva_bind_gpasid(struct iommu_domain *domain,
> > -			   struct device *dev, struct
> > iommu_gpasid_bind_data *data) +int iommu_sva_bind_gpasid(struct
> > iommu_domain *domain, struct device *dev,
> > +						void __user *udata)
> >   {
> > +
> > +	struct iommu_gpasid_bind_data data;
> > +	unsigned long minsz, maxsz;
> > +
> >   	if (unlikely(!domain->ops->sva_bind_gpasid))
> >   		return -ENODEV;
> >   
> > -	return domain->ops->sva_bind_gpasid(domain, dev, data);
> > +	/* Current kernel data size is the max to be copied from
> > user */
> > +	maxsz = sizeof(struct iommu_gpasid_bind_data);
> > +	memset((void *)&data, 0, maxsz);
> > +
> > +	/*
> > +	 * No new spaces can be added before the variable sized
> > union, the
> > +	 * minimum size is the offset to the union.
> > +	 */
> > +	minsz = offsetof(struct iommu_gpasid_bind_data, vendor);
> > +
> > +	/* Copy minsz from user to get flags and argsz */
> > +	if (copy_from_user(&data, udata, minsz))
> > +		return -EFAULT;
> > +
> > +	/* Fields before variable size union is mandatory */
> > +	if (data.argsz < minsz)
> > +		return -EINVAL;
> > +	/*
> > +	 * User might be using a newer UAPI header, we shall let
> > IOMMU vendor
> > +	 * driver decide on what size it needs. Since the guest
> > PASID bind data
> > +	 * can be vendor specific, larger argsz could be the
> > result of extension
> > +	 * for one vendor but it should not affect another vendor.
> > +	 */
> > +	if (data.argsz > maxsz)
> > +		data.argsz = maxsz;
> > +
> > +	/* Copy the remaining user data _after_ minsz */
> > +	if (copy_from_user((void *)&data + minsz, udata + minsz,
> > +				data.argsz - minsz))
> > +		return -EFAULT;
> > +
> > +
> > +	return domain->ops->sva_bind_gpasid(domain, dev, &data);
> >   }
> >   EXPORT_SYMBOL_GPL(iommu_sva_bind_gpasid);
> >   
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 5f0b7859d2eb..a688fea42ae5 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -432,9 +432,10 @@ extern void iommu_detach_device(struct
> > iommu_domain *domain, struct device *dev);
> >   extern int iommu_cache_invalidate(struct iommu_domain *domain,
> >   				  struct device *dev,
> > -				  struct
> > iommu_cache_invalidate_info *inv_info);
> > +				  void __user *uinfo);
> > +
> >   extern int iommu_sva_bind_gpasid(struct iommu_domain *domain,
> > -		struct device *dev, struct iommu_gpasid_bind_data
> > *data);
> > +				struct device *dev, void __user
> > *udata); extern int iommu_sva_unbind_gpasid(struct iommu_domain
> > *domain, struct device *dev, ioasid_t pasid);
> >   extern struct iommu_domain *iommu_get_domain_for_dev(struct
> > device *dev); @@ -1062,7 +1063,7 @@ iommu_cache_invalidate(struct
> > iommu_domain *domain, return -ENODEV;
> >   }
> >   static inline int iommu_sva_bind_gpasid(struct iommu_domain
> > *domain,
> > -				struct device *dev, struct
> > iommu_gpasid_bind_data *data)
> > +				struct device *dev, void __user
> > *udata) {
> >   	return -ENODEV;
> >   }
> >   
> 
> Best regards,
> baolu

[Jacob Pan]