[PATCH AUTOSEL 6.6 32/61] drm/sched: memset() 'job' in drm_sched_job_init()

[Sasha Levin]

From: Philipp Stanner <pstanner at redhat.com>

[ Upstream commit 2320c9e6a768d135c7b0039995182bb1a4e4fd22 ]

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 at redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241021105028.19794-2-pstanner@redhat.com
Reviewed-by: Christian König <christian.koenig at amd.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 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 5a3a622fc672f..fa4652f234718 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -635,6 +635,14 @@ int drm_sched_job_init(struct drm_sched_job *job,
 	if (!entity->rq)
 		return -ENOENT;
 
+	/*
+	 * 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->s_fence = drm_sched_fence_alloc(entity, owner);
 	if (!job->s_fence)
-- 
2.43.0