On Sun, Jan 8, 2023 at 1:13 PM Dmitry Osipenko
<dmitry.osipenko@xxxxxxxxxxxxx> wrote:
>
> drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
> in the dma-buf shmem GEM object getting prematurely freed leading to a
> later use-after-free.
>
> Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Reviewed-by: Rob Clark <robdclark@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index f21f47737817..8b20b41497e8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -624,11 +624,14 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
> int ret;
>
> if (obj->import_attach) {
> - /* Drop the reference drm_gem_mmap_obj() acquired.*/
> - drm_gem_object_put(obj);
> vma->vm_private_data = NULL;
> + ret = dma_buf_mmap(obj->dma_buf, vma, 0);
> +
> + /* Drop the reference drm_gem_mmap_obj() acquired.*/
> + if (!ret)
> + drm_gem_object_put(obj);
>
> - return dma_buf_mmap(obj->dma_buf, vma, 0);
> + return ret;
> }
>
> ret = drm_gem_shmem_get_pages(shmem);
> --
> 2.38.1
>
