drm/sched: avoid killing parent entity on child SIGKILL

commit 9e8b3201c7302d5b522ba3535630bed21cc03c27 upstream.

The DRM scheduler tracks who last uses an entity and when that process
is killed blocks all further submissions to that entity.

The problem is that we didn't track who initially created an entity, so
when a process accidently leaked its file descriptor to a child and
that child got killed, we killed the parent's entities.

Avoid that and instead initialize the entities last user on entity
creation. This also allows to drop the extra NULL check.

Signed-off-by: David Rosca <david.rosca@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4568
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
CC: stable@vger.kernel.org
Acked-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20251015140128.1470-1-christian.koenig@amd.com
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20251015140128.1470-1-christian.koenig@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 3e75fc1f6607225c93b2262cfcd6d7cf456f648f..a9952d86fd3613cf36d44d729f6e44c27b270b91 100644 (file)
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -71,6 +71,7 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
        entity->guilty = guilty;
        entity->num_sched_list = num_sched_list;
        entity->priority = priority;
+       entity->last_user = current->group_leader;
        /*
         * It's perfectly valid to initialize an entity without having a valid
         * scheduler attached. It's just not valid to use the scheduler before it
@@ -315,7 +316,7 @@ long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
 
        /* For killed process disable any more IBs enqueue right now */
        last_user = cmpxchg(&entity->last_user, current->group_leader, NULL);
-       if ((!last_user || last_user == current->group_leader) &&
+       if (last_user == current->group_leader &&
            (current->flags & PF_EXITING) && (current->exit_code == SIGKILL))
                drm_sched_entity_kill(entity);