Re: [PATCH] accel/ivpu: Reject PRIME export of userptr BOs

["Christian König" <christian.koenig@amd.com>]

Hi Zivi,

On 5/8/26 18:28, Ziyi Guo wrote:
>   Userptr BOs wrap pinned user pages in a private dma-buf solely for
>   internal use by the NPU driver. Allowing userspace to re-export such a
>   BO via DRM_IOCTL_PRIME_HANDLE_TO_FD would expose those pages to other
>   drivers through an interface that was never intended to be shared.
> 
>   Override the driver's prime_handle_to_fd callback to detect dma-bufs
>   backed by ivpu_gem_userptr_dmabuf_ops and reject the export with
>   -EINVAL.
> 
> Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>

first of all thanks a lot for pointing that out! The patch which orginally added that somehow slipped through the cracks.

Then @Karol and @Jacek, using DMA-buf like that is a pretty big NO-GO from the DMA-buf side!

Using page which you don't own (especially file system backend ones) in a DMA-buf is absolutely *NOT* something you can do.

I hope that it is not the case here, but if you also allow to mmap() them then you have create a massive security problem which can lead to random file system corruptions.

Regards,
Christian.

> ---
>  drivers/accel/ivpu/ivpu_drv.c         |  1 +
>  drivers/accel/ivpu/ivpu_gem.c         | 28 +++++++++++++++++++++++++++
>  drivers/accel/ivpu/ivpu_gem.h         |  3 +++
>  drivers/accel/ivpu/ivpu_gem_userptr.c |  5 +++++
>  4 files changed, 37 insertions(+)
> 
> diff --git a/drivers/accel/ivpu/ivpu_drv.c b/drivers/accel/ivpu/ivpu_drv.c
> index 2801378e3e19..086d4c769b33 100644
> --- a/drivers/accel/ivpu/ivpu_drv.c
> +++ b/drivers/accel/ivpu/ivpu_drv.c
> @@ -545,6 +545,7 @@ static const struct drm_driver driver = {
> 
>         .gem_create_object = ivpu_gem_create_object,
>         .gem_prime_import = ivpu_gem_prime_import,
> +       .prime_handle_to_fd = ivpu_gem_prime_handle_to_fd,
> 
>         .ioctls = ivpu_drm_ioctls,
>         .num_ioctls = ARRAY_SIZE(ivpu_drm_ioctls),
> diff --git a/drivers/accel/ivpu/ivpu_gem.c b/drivers/accel/ivpu/ivpu_gem.c
> index 4f2005a8d496..82079f372b39 100644
> --- a/drivers/accel/ivpu/ivpu_gem.c
> +++ b/drivers/accel/ivpu/ivpu_gem.c
> @@ -12,6 +12,7 @@
>  #include <drm/drm_cache.h>
>  #include <drm/drm_debugfs.h>
>  #include <drm/drm_file.h>
> +#include <drm/drm_prime.h>
>  #include <drm/drm_utils.h>
> 
>  #include "ivpu_drv.h"
> @@ -249,6 +250,33 @@ struct drm_gem_object *ivpu_gem_prime_import(struct drm_device *dev,
>         return ERR_PTR(ret);
>  }
> 
> +int ivpu_gem_prime_handle_to_fd(struct drm_device *dev, struct drm_file *file_priv,
> +                               u32 handle, u32 flags, int *prime_fd)
> +{
> +       struct ivpu_device *vdev = to_ivpu_device(dev);
> +       struct dma_buf *dmabuf;
> +       int fd;
> +
> +       dmabuf = drm_gem_prime_handle_to_dmabuf(dev, file_priv, handle, flags);
> +       if (IS_ERR(dmabuf))
> +               return PTR_ERR(dmabuf);
> +
> +       if (ivpu_gem_is_userptr_dma_buf(dmabuf)) {
> +               ivpu_dbg(vdev, IOCTL, "Exporting userptr BO is not allowed\n");
> +               dma_buf_put(dmabuf);
> +               return -EINVAL;
> +       }
> +
> +       fd = dma_buf_fd(dmabuf, flags);
> +       if (fd < 0) {
> +               dma_buf_put(dmabuf);
> +               return fd;
> +       }
> +
> +       *prime_fd = fd;
> +       return 0;
> +}
> +
>  static struct ivpu_bo *ivpu_bo_alloc(struct ivpu_device *vdev, u64 size, u32 flags)
>  {
>         struct drm_gem_shmem_object *shmem;
> diff --git a/drivers/accel/ivpu/ivpu_gem.h b/drivers/accel/ivpu/ivpu_gem.h
> index 0c3350f22b55..bfd15ce02354 100644
> --- a/drivers/accel/ivpu/ivpu_gem.h
> +++ b/drivers/accel/ivpu/ivpu_gem.h
> @@ -29,6 +29,9 @@ void ivpu_bo_unbind_all_bos_from_context(struct ivpu_device *vdev, struct ivpu_m
> 
>  struct drm_gem_object *ivpu_gem_create_object(struct drm_device *dev, size_t size);
>  struct drm_gem_object *ivpu_gem_prime_import(struct drm_device *dev, struct dma_buf *dma_buf);
> +int ivpu_gem_prime_handle_to_fd(struct drm_device *dev, struct drm_file *file_priv,
> +                               u32 handle, u32 flags, int *prime_fd);
> +bool ivpu_gem_is_userptr_dma_buf(struct dma_buf *dma_buf);
>  struct ivpu_bo *ivpu_bo_create(struct ivpu_device *vdev, struct ivpu_mmu_context *ctx,
>                                struct ivpu_addr_range *range, u64 size, u32 flags);
>  struct ivpu_bo *ivpu_bo_create_runtime(struct ivpu_device *vdev, u64 addr, u64 size, u32 flags);
> diff --git a/drivers/accel/ivpu/ivpu_gem_userptr.c b/drivers/accel/ivpu/ivpu_gem_userptr.c
> index 7cbf3a4cdc73..45eabea5961e 100644
> --- a/drivers/accel/ivpu/ivpu_gem_userptr.c
> +++ b/drivers/accel/ivpu/ivpu_gem_userptr.c
> @@ -61,6 +61,11 @@ static const struct dma_buf_ops ivpu_gem_userptr_dmabuf_ops = {
>         .release = ivpu_gem_userptr_dmabuf_release,
>  };
> 
> +bool ivpu_gem_is_userptr_dma_buf(struct dma_buf *dma_buf)
> +{
> +       return dma_buf->ops == &ivpu_gem_userptr_dmabuf_ops;
> +}
> +
>  static struct dma_buf *
>  ivpu_create_userptr_dmabuf(struct ivpu_device *vdev, void __user *user_ptr,
>                            size_t size, uint32_t flags)
> --
> 2.34.1
>