Re: [PATCH 2/3] iommufd: Add check on user response code

[Jason Gunthorpe <jgg@ziepe.ca>]

On Wed, Jul 10, 2024 at 04:33:40PM +0800, Lu Baolu wrote:
> The response code from user space is only allowed to be SUCCESS or
> INVALID. All other values are treated by the device as a response
> code of Response Failure according to PCI spec, section 10.4.2.1.
> This response disables the Page Request Interface for the Function.
> 
> Add a check in iommufd_fault_fops_write() to avoid invalid response
> code.
> 
> Fixes: 07838f7fd529 ("iommufd: Add iommufd fault object")
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/iommu/iommufd/fault.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/iommufd/fault.c b/drivers/iommu/iommufd/fault.c
> index 54d6cd20a673..044b9b97da31 100644
> --- a/drivers/iommu/iommufd/fault.c
> +++ b/drivers/iommu/iommufd/fault.c
> @@ -305,6 +305,12 @@ static ssize_t iommufd_fault_fops_write(struct file *filep, const char __user *b
>  		if (rc)
>  			break;
>  
> +		if (response.code != IOMMUFD_PAGE_RESP_SUCCESS &&
> +		    response.code != IOMMUFD_PAGE_RESP_INVALID) {
> +			rc = -EINVAL;
> +			break;
> +		}


I added this:

		static_assert(IOMMUFD_PAGE_RESP_SUCCESS ==
			      IOMMU_PAGE_RESP_SUCCESS);
		static_assert(IOMMUFD_PAGE_RESP_INVALID ==
			      IOMMU_PAGE_RESP_INVALID);

As well

Jason