In the Linux kernel, the following vulnerability has been resolved:
drm/nouveau/uvmm: fix NULL deref unwinding an OP_MAP_SPARSE op
Each bind_job_op is zeroed by kzalloc_obj() in bind_job_op_from_uop(),
and the OP_MAP_SPARSE case in nouveau_uvmm_bind_job_submit() only creates
a region, so op->ops stays NULL for a successfully processed sparse map.
If a later op in the same job fails, the reverse unwind loop revisits that
op and calls drm_gpuva_ops_free(&uvmm->base, op->ops) unconditionally.
drm_gpuva_ops_free() dereferences its argument right away
(list_for_each_entry_safe on &ops->list), so a NULL op->ops oopses. The
path is reachable by any render-node fd holder, since NOUVEAU_VM_BIND is
DRM_RENDER_ALLOW.
Guard the free with IS_ERR_OR_NULL(), as nouveau_uvmm_bind_job_cleanup()
already does for the identical free.
