Re: [PATCH v5 4/5] iommu/uapi: Handle data and argsz filled by users

Auger Eric
2020-07-17T15:58:24Z

Hi Jacob,
On 7/16/20 8:45 PM, Jacob Pan wrote:

Could you share a branch? I was not able to apply this on either
iommu/next or master?

> IOMMU UAPI data has a user filled argsz field which indicates the data
> length comes with the API call.
s/ comes with the API call/ of the structure
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.
s/results/resulting
> Backward compatibility is ensured based on size and flags checking.
flags is missing in iommu_cache_invalidate_info.
>
> 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
s/privided/provided
> + * make sure no reserved fields or unused flags are not set. This is to ensure
s/not// ?
> + * 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)
increased version number?
> + 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])
padding has become "__u8 padding[6];" in 2/5

> + 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 */
s/requires/require
> + 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;
> +
> + /* 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);
>
> -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++) {
now 8
> + 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);
> +
> + /*
> + * 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))
> + return -EFAULT;
> +
> + return iommu_check_bind_data(data);
> +}
> +
> +int iommu_sva_bind_gpasid(struct iommu_domain *domain, struct device *dev,
> + void __user *udata)
change of proto not described in the commit msg
> +{
> +
> + struct iommu_gpasid_bind_data data;
> + 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)
This change and the introduction of iommu_uapi_sva_unbind_gpasid look
unrelated to this patch, at least not described in the commit msg.
> {
> 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;
> + 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,
> 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_uapi_sva_unbind_gpasid(struct iommu_domain *domain,
> + struct device *dev, void __user *udata);
not motivated in the commit msg. I think change of proto and addition of
iommu_sva_unbind_gpasid would deserve a separate patch.
> 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,
> + struct device *dev,
> + struct iommu_gpasid_bind_data *data)
> {
> return -ENODEV;
> }
>

Thanks

Eric