It already happend a few times that patches slipped through which implemented access to an entity through a job that was already removed from the entities queue. Since jobs and entities might have different lifecycles, this can potentially cause UAF bugs. In order to make it obvious that a jobs entity pointer shouldn't be accessed after drm_sched_entity_pop_job() was called successfully, set the jobs entity pointer to NULL once the job is removed from the entity queue. Moreover, debugging a potential NULL pointer dereference is way easier than potentially corrupted memory through a UAF. Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx> --- I'm aware that drivers could already use job->entity in arbitrary places, since they in control of when the entity is actually freed. A quick grep didn't give me any results where this would actually be the case, however maybe I also just didn't catch it. If, therefore, we don't want to set job->entity to NULL I think we should at least add a comment somewhere. --- drivers/gpu/drm/scheduler/sched_entity.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index 15d04a0ec623..a9c6118e534b 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -448,6 +448,12 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity) drm_sched_rq_update_fifo(entity, next->submit_ts); } + /* Jobs and entities might have different lifecycles. Since we're + * removing the job from the entities queue, set the jobs entity pointer + * to NULL to prevent any future access of the entity through this job. + */ + sched_job->entity = NULL; + return sched_job; } -- 2.39.2
