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> --- drivers/gpu/drm/scheduler/sched_entity.c | 6 ++++++ drivers/gpu/drm/scheduler/sched_main.c | 4 ++++ 2 files changed, 10 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; } diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index 9b16480686f6..e89a3e469cd5 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -42,6 +42,10 @@ * the hardware. * * The jobs in a entity are always scheduled in the order that they were pushed. + * + * Note that once a job was taken from the entities queue and pushed to the + * hardware, i.e. the pending queue, the entity must not be referenced anymore + * through the jobs entity pointer. */ #include <linux/kthread.h> -- 2.39.2
