drm/xe: Don't free job in TDR

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: drm/xe/kernel#2811


Cc: Matthew Auld <matthew.auld@intel.com>
Fixes: e275d61c ("drm/xe/guc: Handle timing out of signaled jobs gracefully")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003001657.3517883-3-matthew.brost@intel.com

drivers/gpu/drm/xe/xe_guc_submit.c

@@ -1105,10 +1105,13 @@ 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;
 	}