Messages in this thread | | | Date | Fri, 31 Mar 2023 07:59:29 +0200 | Subject | Re: [PATCH] drm/scheduler: set entity to NULL in drm_sched_entity_pop_job() | From | Christian König <> |
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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@redhat.com>
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; > } >
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