*PING* On Tue, 2024-08-06 at 16:38 +0200, Philipp Stanner wrote: > drm_sched_job_init() has no control over how users allocate struct > drm_sched_job. Unfortunately, the function can also not set some > struct > members such as job->sched. > > This could theoretically lead to UB by users dereferencing the > struct's > pointer members too early. > > It is easier to debug such issues if these pointers are initialized > to > NULL, so dereferencing them causes a NULL pointer exception. > Accordingly, drm_sched_entity_init() does precisely that and > initializes > its struct with memset(). > > Initialize parameter "job" to 0 in drm_sched_job_init(). > > Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx> > --- > Hi all, > I did some experiments with the scheduler recently and am trying to > make > the documentation and bits of the code more bullet proof. > > I tested the performance of v6.11-rc2 with and without this memset() > by > creating 1e6 jobs and found no performance regression. > > Cheers, > P. > --- > drivers/gpu/drm/scheduler/sched_main.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c > b/drivers/gpu/drm/scheduler/sched_main.c > index 76969f9c59c2..1498ee3cbf39 100644 > --- a/drivers/gpu/drm/scheduler/sched_main.c > +++ b/drivers/gpu/drm/scheduler/sched_main.c > @@ -936,6 +936,14 @@ int drm_sched_job_init(struct drm_sched_job > *job, > return -EINVAL; > } > > + /* > + * We don't know for sure how the user has allocated. Thus, > zero the > + * struct so that unallowed (i.e., too early) usage of > pointers that > + * this function does not set is guaranteed to lead to a > NULL pointer > + * exception instead of UB. > + */ > + memset(job, 0, sizeof(*job)); > + > job->entity = entity; > job->credits = credits; > job->s_fence = drm_sched_fence_alloc(entity, owner);
