[PATCH 2/2] drm/xe: Don't free job in TDR

[Matthew Brost]

Freeing job in TDR is not safe as TDR can pass the run_job thread
resulting in UAF. It is only safe for free job to naturally be called by
the scheduler. Rather free job in TDR, add to pending list.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2811
Cc: Matthew Auld <matthew.auld at intel.com>
Fixes: e275d61c5f3f ("drm/xe/guc: Handle timing out of signaled jobs gracefully")
Signed-off-by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_guc_submit.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
index 80062e1d3f66..9ecd1661c1b5 100644
--- a/drivers/gpu/drm/xe/xe_guc_submit.c
+++ b/drivers/gpu/drm/xe/xe_guc_submit.c
@@ -1106,10 +1106,13 @@ guc_exec_queue_timedout_job(struct drm_sched_job *drm_job)
 
 	/*
 	 * TDR has fired before free job worker. Common if exec queue
-	 * immediately closed after last fence signaled.
+	 * immediately closed after last fence signaled. Add back to pending
+	 * list so job can be freed and kick scheduler ensuring free job is not
+	 * lost.
 	 */
 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &job->fence->flags)) {
-		guc_exec_queue_free_job(drm_job);
+		xe_sched_add_pending_job(sched, job);
+		xe_sched_submission_start(sched);
 
 		return DRM_GPU_SCHED_STAT_NOMINAL;
 	}
-- 
2.34.1