Re: [syzbot] [block?] BUG: corrupted list in loop_process_work

[Hillf Danton]

On Fri, 14 Feb 2025 11:58:24 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    c674aa7c289e Add linux-next specific files for 20250212
> git tree:       linux-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17e18aa4580000

#syz test

--- x/drivers/block/loop.c
+++ y/drivers/block/loop.c
@@ -1974,7 +1974,8 @@ static void loop_process_work(struct loo
 	 */
 	if (worker && !work_pending(&worker->work)) {
 		worker->last_ran_at = jiffies;
-		list_add_tail(&worker->idle_list, &lo->idle_worker_list);
+		if (list_empty(&worker->idle_list))
+			list_add_tail(&worker->idle_list, &lo->idle_worker_list);
 		loop_set_timer(lo);
 	}
 	spin_unlock_irq(&lo->lo_work_lock);
--