From 1e1d3574e69f70b848f9d50eca2c5ff04931b7ba Mon Sep 17 00:00:00 2001 From: Asahi Lina Date: Thu, 6 Apr 2023 01:37:39 +0900 Subject: [PATCH] drm/scheduler: Fix UAF race in drm_sched_entity_push_job() After a job is pushed into the queue, it is owned by the scheduler core and may be freed at any time, so we can't write nor read the submit timestamp after that point. Fixes oopses observed with the drm/asahi driver, found with kASAN. Signed-off-by: Asahi Lina Link: https://lore.kernel.org/r/20230406-scheduler-uaf-2-v1-1-972531cf0a81@asahilina.net Reviewed-by: Luben Tuikov Signed-off-by: Luben Tuikov --- drivers/gpu/drm/scheduler/sched_entity.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index 15d04a0..e0a8890 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -507,12 +507,19 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job) { struct drm_sched_entity *entity = sched_job->entity; bool first; + ktime_t submit_ts; trace_drm_sched_job(sched_job, entity); atomic_inc(entity->rq->sched->score); WRITE_ONCE(entity->last_user, current->group_leader); + + /* + * After the sched_job is pushed into the entity queue, it may be + * completed and freed up at any time. We can no longer access it. + * Make sure to set the submit_ts first, to avoid a race. + */ + sched_job->submit_ts = submit_ts = ktime_get(); first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node); - sched_job->submit_ts = ktime_get(); /* first job wakes up scheduler */ if (first) { @@ -529,7 +536,7 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job) spin_unlock(&entity->rq_lock); if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) - drm_sched_rq_update_fifo(entity, sched_job->submit_ts); + drm_sched_rq_update_fifo(entity, submit_ts); drm_sched_wakeup(entity->rq->sched); } -- 2.7.4