Re: [PATCH v2 1/3] vfio/type1: sanitize for overflow using check_*_overflow

Jason Gunthorpe
2025-10-08T12:19:33Z

On Tue, Oct 07, 2025 at 09:08:46PM -0700, Alex Mastro wrote:
> Adopt check_*_overflow functions to clearly express overflow check
> intent.
>
> Signed-off-by: Alex Mastro <amastro@fb.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 54 ++++++++++++++++++++++++++++++++---------
> 1 file changed, 43 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index f8d68fe77b41..b510ef3f397b 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -37,6 +37,7 @@
> #include <linux/vfio.h>
> #include <linux/workqueue.h>
> #include <linux/notifier.h>
> +#include <linux/overflow.h>
> #include "vfio.h"
>
> #define DRIVER_VERSION "0.2"
> @@ -825,14 +826,25 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
> unsigned long remote_vaddr;
> struct vfio_dma *dma;
> bool do_accounting;
> + dma_addr_t iova_end;
> + size_t iova_size;
>
> - if (!iommu || !pages)
> + if (!iommu || !pages || npage < 0)
> return -EINVAL;
>
> /* Supported for v2 version only */
> if (!iommu->v2)
> return -EACCES;
>
> + if (npage == 0)
> + return 0;
> +
> + if (check_mul_overflow(npage, PAGE_SIZE, &iova_size))
> + return -EINVAL;

-EOVERFLOW and everywhere else

> +
> + if (check_add_overflow(user_iova, iova_size - 1, &iova_end))
> + return -EINVAL;

Let's be consistent with iommufd/etc, 'end' is start+size 'last' is start+size-1

Otherwise it is super confusing :(

Jason