Re: [PATCH rc] iommu: Validate the PASID in iommu_attach_device_pasid()

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

On 2024/3/27 21:41, Jason Gunthorpe wrote:
> The SVA code checks that the PASID is valid for the device when assigning
> the PASID to the MM, but the normal PAGING related path does not check it.
> > Devices that don't support PASID or PASID values too large for the device
> should not invoke the driver callback. The drivers should rely on the
> core code for this enforcement.

I agree it is reasonable to enforce it in the core. But I'm not sure if a
fix tag is needed or not. As far as I know, intel iommu driver supports 
attaching both the SVA and DMA type (PAGING) domain to pasid. Intel iommu
driver checks the max pasid in intel_pasid_get_entry() of 
drivers/iommu/intel/pasid.c.
I'm not sure about ARM and AMD side, if the two drivers only support SVA
domain, and have the max pasid check. Then fix tag may be not necessary as
all the related paths are in good shape on the max pasid check before this
fix. :)

> Fixes: 16603704559c7a68 ("iommu: Add attach/detach_dev_pasid iommu interfaces")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>   drivers/iommu/iommu.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 098869007c69e5..a95a483def2d2a 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -3354,6 +3354,7 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
>   {
>   	/* Caller must be a probed driver on dev */
>   	struct iommu_group *group = dev->iommu_group;
> +	struct group_device *device;
>   	void *curr;
>   	int ret;
>   
> @@ -3363,10 +3364,18 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
>   	if (!group)
>   		return -ENODEV;
>   
> -	if (!dev_has_iommu(dev) || dev_iommu_ops(dev) != domain->owner)
> +	if (!dev_has_iommu(dev) || dev_iommu_ops(dev) != domain->owner ||
> +	    pasid == IOMMU_NO_PASID)

perhaps this can be a separate patch as it means this API does not support
NO_PASID attachment.

>   		return -EINVAL;
>   
>   	mutex_lock(&group->mutex);
> +	for_each_group_device(group, device) {
> +		if (pasid >= device->dev->iommu->max_pasids) {
> +			ret = -EINVAL;
> +			goto out_unlock;
> +		}
> +	}
> +
>   	curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain, GFP_KERNEL);
>   	if (curr) {
>   		ret = xa_err(curr) ? : -EBUSY;
> 
> base-commit: 4cece764965020c22cff7665b18a012006359095

Overall looks good to me although one nit.

-- 
Regards,
Yi Liu