[PATCH] vfio/type1: Fix unmap overflow off-by-one

[PATCH] vfio/type1: Fix unmap overflow off-by-one

[Alex Williamson]

The below referenced commit adds a test for integer overflow, but in
doing so prevents the unmap ioctl from ever including the last page of
the address space.  Subtract one to compare to the last address of the
unmap to avoid the overflow and wrap-around.

Fixes: 71a7d3d78e3c ("vfio/type1: silence integer overflow warning")
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1662291
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Pei Zhang <pezhang@redhat.com>
Debugged-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio_iommu_type1.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 7651cfb14836..73652e21efec 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -878,7 +878,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		return -EINVAL;
 	if (!unmap->size || unmap->size & mask)
 		return -EINVAL;
-	if (unmap->iova + unmap->size < unmap->iova ||
+	if (unmap->iova + unmap->size - 1 < unmap->iova ||
 	    unmap->size > SIZE_MAX)
 		return -EINVAL;
 

Re: [PATCH] vfio/type1: Fix unmap overflow off-by-one

[Dan Carpenter]

Yeah, sorry about that.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>

regards,
dan carpenter

Re: [PATCH] vfio/type1: Fix unmap overflow off-by-one

[Peter Xu]

On Tue, Jan 08, 2019 at 09:40:06AM -0700, Alex Williamson wrote:
> The below referenced commit adds a test for integer overflow, but in
> doing so prevents the unmap ioctl from ever including the last page of
> the address space.  Subtract one to compare to the last address of the
> unmap to avoid the overflow and wrap-around.
> 
> Fixes: 71a7d3d78e3c ("vfio/type1: silence integer overflow warning")
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1662291
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Reported-by: Pei Zhang <pezhang@redhat.com>
> Debugged-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

I tested this against the QEMU reboot error and it works.

Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Peter Xu <peterx@redhat.com>

Thanks,

> ---
>  drivers/vfio/vfio_iommu_type1.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 7651cfb14836..73652e21efec 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -878,7 +878,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  		return -EINVAL;
>  	if (!unmap->size || unmap->size & mask)
>  		return -EINVAL;
> -	if (unmap->iova + unmap->size < unmap->iova ||
> +	if (unmap->iova + unmap->size - 1 < unmap->iova ||
>  	    unmap->size > SIZE_MAX)
>  		return -EINVAL;
>  
> 

-- 
Peter Xu

Re: [PATCH] vfio/type1: Fix unmap overflow off-by-one

[Cornelia Huck]

On Tue, 08 Jan 2019 09:40:06 -0700
Alex Williamson <alex.williamson@redhat.com> wrote:

> The below referenced commit adds a test for integer overflow, but in
> doing so prevents the unmap ioctl from ever including the last page of
> the address space.  Subtract one to compare to the last address of the
> unmap to avoid the overflow and wrap-around.
> 
> Fixes: 71a7d3d78e3c ("vfio/type1: silence integer overflow warning")
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1662291
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Reported-by: Pei Zhang <pezhang@redhat.com>
> Debugged-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>