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    SubjectRe: [PATCH v5 4/5] iommu/uapi: Handle data and argsz filled by users
    On Thu, 16 Jul 2020 11:45:16 -0700
    Jacob Pan <jacob.jun.pan@linux.intel.com> 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.
    >
    > This patch adds sanity checks in the IOMMU layer. In addition to argsz,
    > reserved/unused fields in padding, flags, and version are also checked.
    > Details are documented in Documentation/userspace-api/iommu.rst
    >
    > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
    > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
    > ---
    > drivers/iommu/iommu.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++++--
    > include/linux/iommu.h | 20 ++++--
    > 2 files changed, 200 insertions(+), 12 deletions(-)
    >
    > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
    > index d43120eb1dc5..fe30a940d19e 100644
    > --- a/drivers/iommu/iommu.c
    > +++ b/drivers/iommu/iommu.c
    > @@ -1950,36 +1950,214 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
    > }
    > EXPORT_SYMBOL_GPL(iommu_attach_device);
    >
    > +/*
    > + * Check flags and other user privided data for valid combinations. We also
    > + * make sure no reserved fields or unused flags are not set. This is to ensure
    > + * not breaking userspace in the future when these fields or flags are used.
    > + */
    > +static int iommu_check_cache_invl_data(struct iommu_cache_invalidate_info *info)
    > +{
    > + u32 mask;
    > +
    > + if (info->version != IOMMU_CACHE_INVALIDATE_INFO_VERSION_1)
    > + return -EINVAL;
    > +
    > + mask = (1 << IOMMU_CACHE_INV_TYPE_NR) - 1;
    > + if (info->cache & ~mask)
    > + return -EINVAL;
    > +
    > + if (info->granularity >= IOMMU_INV_GRANU_NR)
    > + return -EINVAL;
    > +
    > + switch (info->granularity) {
    > + case IOMMU_INV_GRANU_ADDR:
    > + mask = IOMMU_INV_ADDR_FLAGS_PASID |
    > + IOMMU_INV_ADDR_FLAGS_ARCHID |
    > + IOMMU_INV_ADDR_FLAGS_LEAF;
    > +
    > + if (info->granu.addr_info.flags & ~mask)
    > + return -EINVAL;
    > + break;
    > + case IOMMU_INV_GRANU_PASID:
    > + mask = IOMMU_INV_PASID_FLAGS_PASID |
    > + IOMMU_INV_PASID_FLAGS_ARCHID;
    > + if (info->granu.pasid_info.flags & ~mask)
    > + return -EINVAL;
    > +
    > + break;
    > + case IOMMU_INV_GRANU_DOMAIN:
    > + /* No flags to check */
    > + break;
    > + default:
    > + return -EINVAL;
    > + }
    > +
    > + if (info->padding[0] || info->padding[1])
    > + return -EINVAL;
    > +
    > + return 0;
    > +}
    > +
    > int iommu_cache_invalidate(struct iommu_domain *domain, struct device *dev,
    > - struct iommu_cache_invalidate_info *inv_info)
    > + void __user *uinfo)
    > {
    > + struct iommu_cache_invalidate_info inv_info = { 0 };
    > + u32 minsz, maxsz;
    > + int ret = 0;
    > +
    > 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);
    > +
    > + /*
    > + * 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;
    > +
    > + /* PASID and address granu requires additional info beyond minsz */
    > + if (inv_info.argsz == minsz &&
    > + ((inv_info.granularity == IOMMU_INV_GRANU_PASID) ||
    > + (inv_info.granularity == IOMMU_INV_GRANU_ADDR)))
    > + return -EINVAL;
    > + /*
    > + * User might be using a newer UAPI header which has a larger data
    > + * size, we shall support the existing flags within the current
    > + * size. Copy the remaining user data _after_ minsz but not more
    > + * than the current kernel supported size.
    > + */
    > + if (copy_from_user((void *)&inv_info + minsz, uinfo + minsz,
    > + min(inv_info.argsz, maxsz) - minsz))
    > + return -EFAULT;

    To further clarify previous comments about maxsz usage:

    s/maxsz/sizeof(inv_info)/

    > +
    > + /* Now the argsz is validated, check the content */
    > + ret = iommu_check_cache_invl_data(&inv_info);
    > + if (ret)
    > + return ret;
    > +
    > + return domain->ops->cache_invalidate(domain, dev, &inv_info);
    > }
    > EXPORT_SYMBOL_GPL(iommu_cache_invalidate);


    Remainder of comments for above provided in 1/5.

    >
    > -int iommu_sva_bind_gpasid(struct iommu_domain *domain,
    > - struct device *dev, struct iommu_gpasid_bind_data *data)
    > +
    > +static int iommu_check_bind_data(struct iommu_gpasid_bind_data *data)
    > {
    > + u32 mask;
    > + int i;
    > +
    > + if (data->version != IOMMU_GPASID_BIND_VERSION_1)
    > + return -EINVAL;
    > +
    > + /* Check all supported format, for now just VT-d */
    > + mask = IOMMU_PASID_FORMAT_INTEL_VTD;
    > + if (data->format & ~mask)
    > + return -EINVAL;
    > +
    > + /* Check all flags */
    > + mask = IOMMU_SVA_GPASID_VAL;
    > + if (data->flags & ~mask)
    > + return -EINVAL;
    > +
    > + /* Check reserved padding fields */
    > + for (i = 0; i < 12; i++) {
    > + if (data->padding[i])
    > + return -EINVAL;
    > + }
    > +
    > + return 0;
    > +}
    > +
    > +static int iommu_sva_prepare_bind_data(void __user *udata,
    > + struct iommu_gpasid_bind_data *data)
    > +{
    > + u32 minsz, maxsz;
    > +
    > + /* Current kernel data size is the max to be copied from user */
    > + maxsz = sizeof(struct iommu_gpasid_bind_data);
    > + memset((void *)data, 0, maxsz);

    Let the caller pass a zero'd structure.

    > +
    > + /*
    > + * 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.
    > + * Copy the remaining user data _after_ minsz
    > + */
    > + if (copy_from_user((void *)data + minsz, udata + minsz,
    > + min(data->argsz, maxsz) - minsz))


    We could replace maxsz entirely with sizeof(*data)

    > + return -EFAULT;
    > +
    > + return iommu_check_bind_data(data);
    > +}
    > +
    > +int iommu_sva_bind_gpasid(struct iommu_domain *domain, struct device *dev,
    > + void __user *udata)

    iommu_uapi_sva_bind_gpasid(...

    > +{
    > +
    > + struct iommu_gpasid_bind_data data;

    = { 0 }

    > + int ret;
    > +
    > if (unlikely(!domain->ops->sva_bind_gpasid))
    > return -ENODEV;
    >
    > - return domain->ops->sva_bind_gpasid(domain, dev, data);
    > + ret = iommu_sva_prepare_bind_data(udata, &data);
    > + if (ret)
    > + return ret;
    > +
    > + return domain->ops->sva_bind_gpasid(domain, dev, &data);
    > }
    > EXPORT_SYMBOL_GPL(iommu_sva_bind_gpasid);
    >
    > int iommu_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
    > - ioasid_t pasid)
    > + struct iommu_gpasid_bind_data *data)
    > {
    > if (unlikely(!domain->ops->sva_unbind_gpasid))
    > return -ENODEV;
    >
    > - return domain->ops->sva_unbind_gpasid(dev, pasid);
    > + return domain->ops->sva_unbind_gpasid(dev, data->hpasid);
    > }
    > EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
    >
    > +int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain, struct device *dev,
    > + void __user *udata)
    > +{
    > + struct iommu_gpasid_bind_data data;

    = { 0 };

    > + int ret;
    > +
    > + if (unlikely(!domain->ops->sva_bind_gpasid))
    > + return -ENODEV;
    > +
    > + ret = iommu_sva_prepare_bind_data(udata, &data);
    > + if (ret)
    > + return ret;
    > +
    > + return iommu_sva_unbind_gpasid(domain, dev, &data);
    > +}
    > +EXPORT_SYMBOL_GPL(iommu_uapi_sva_unbind_gpasid);
    > +
    > static void __iommu_detach_device(struct iommu_domain *domain,
    > struct device *dev)
    > {
    > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
    > index 5f0b7859d2eb..439f34a7b5b2 100644
    > --- a/include/linux/iommu.h
    > +++ b/include/linux/iommu.h
    > @@ -432,11 +432,14 @@ extern void iommu_detach_device(struct iommu_domain *domain,
    > struct device *dev);
    > extern int iommu_cache_invalidate(struct iommu_domain *domain,

    uapi

    > struct device *dev,
    > - struct iommu_cache_invalidate_info *inv_info);
    > + void __user *uinfo);
    > +
    > extern int iommu_sva_bind_gpasid(struct iommu_domain *domain,

    uapi

    > - struct device *dev, struct iommu_gpasid_bind_data *data);
    > + struct device *dev, void __user *udata);
    > +extern int iommu_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
    > + struct device *dev, void __user *udata);
    > extern int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
    > - struct device *dev, ioasid_t pasid);
    > + struct device *dev, struct iommu_gpasid_bind_data *data);
    > extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
    > extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
    > extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
    > @@ -1062,13 +1065,20 @@ 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;
    > }
    >
    > static inline int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
    > - struct device *dev, int pasid)
    > + struct device *dev, void __user *udata)
    > +{
    > + return -ENODEV;
    > +}
    > +
    > +static inline int __iommu_sva_unbind_gpasid(struct iommu_domain *domain,


    These don't match the previous semantics. Thanks,

    Alex

    > + struct device *dev,
    > + struct iommu_gpasid_bind_data *data)
    > {
    > return -ENODEV;
    > }

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