Re: [PATCH 1/2] vfio/ccw: Add length to DMA_UNMAP checks

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 7/26/22 11:01 AM, Eric Farman wrote:
> As pointed out with the simplification of the
> VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier [1], the length
> parameter was never used to check against the pinned
> pages.
> 
> Let's correct that, and see if a page is within the
> affected range instead of simply the first page of
> the range.
> 
> [1] https://lore.kernel.org/kvm/20220720170457.39cda0d0.alex.williamson@redhat.com/
> 
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
>   drivers/s390/cio/vfio_ccw_cp.c  | 11 +++++++----
>   drivers/s390/cio/vfio_ccw_cp.h  |  2 +-
>   drivers/s390/cio/vfio_ccw_ops.c |  2 +-
>   3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index 8963f452f963..f15b5114abd1 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -170,12 +170,14 @@ static void page_array_unpin_free(struct page_array *pa, struct vfio_device *vde
>   	kfree(pa->pa_iova);
>   }
>   
> -static bool page_array_iova_pinned(struct page_array *pa, unsigned long iova)
> +static bool page_array_iova_pinned(struct page_array *pa, unsigned long iova,
> +				   unsigned long length)
>   {
>   	int i;
>   
>   	for (i = 0; i < pa->pa_nr; i++)
> -		if (pa->pa_iova[i] == iova)
> +		if (pa->pa_iova[i] >= iova &&
> +		    pa->pa_iova[i] <= iova + length)

For the sake of completeness, I think you want to be checking to make 
sure the end of the page is also within the range, not just the start?

if (pa->pa_iova[i] >= iova &&
     pa->pa_iova[i] + PAGE_SIZE <= iova + length)