On 9/30/26 11:38, Jesse Zhang wrote:
> amdgpu_userq_get_doorbell_index() pins any BO passed as doorbell_handle
> into the doorbell domain. For a regular BO, TTM moves it with
> ttm_bo_move_null() and its contents are lost. Since an importer on the
> same device gets the exporter's GEM object, a client can do this to a
> buffer another client shared with it.
>
> Reject BOs that were not created in the doorbell domain.
>
> v2: drop the error message, use a local abo variable (Christian)
>
> Fixes: f09c1e6077ab ("drm/amdgpu: generate doorbell index for userqueue")
> Signed-off-by: Jesse Zhang <[email protected]>
Reviewed-by: Christian König <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
> index 89e03d3a930c..5a922f283743 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
> @@ -469,6 +469,7 @@ amdgpu_userq_get_doorbell_index(struct amdgpu_userq_mgr
> *uq_mgr,
> u64 doorbell_index;
> struct drm_gem_object *gobj;
> struct amdgpu_userq_obj *db_obj = db_info->db_obj;
> + struct amdgpu_bo *abo;
> int r, db_size;
>
> gobj = drm_gem_object_lookup(filp, db_info->doorbell_handle);
> @@ -477,7 +478,17 @@ amdgpu_userq_get_doorbell_index(struct amdgpu_userq_mgr
> *uq_mgr,
> return -EINVAL;
> }
>
> - db_obj->obj = amdgpu_bo_ref(gem_to_amdgpu_bo(gobj));
> + /*
> + * Pinning a regular BO into the doorbell domain would discard its
> + * contents, possibly those of a buffer shared by another client.
> + */
> + abo = gem_to_amdgpu_bo(gobj);
> + if (!(abo->preferred_domains & AMDGPU_GEM_DOMAIN_DOORBELL)) {
> + drm_gem_object_put(gobj);
> + return -EINVAL;
> + }
> +
> + db_obj->obj = amdgpu_bo_ref(abo);
> drm_gem_object_put(gobj);
>
> r = amdgpu_bo_reserve(db_obj->obj, true);
