Am 31.03.23 um 02:06 schrieb Danilo Krummrich:
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>
In general "YES PLEASE!", but I fear that this will break amdgpus reset
sequence.
On the other hand when amdgpu still relies on that pointer it's clearly
a bug (which I pointed out tons of times before).
Luben any opinion on that? Could you drive cleaning that up as well?
Thanks,
Christian.
---
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;
}
