linux-kernel - Re: [syzbot] [net] [virt] INFO: task hung in __vhost_worker

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Message-ID: <20250901013758.6300-1-hdanton@sina.com>
Date: Mon,  1 Sep 2025 09:37:57 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+7f3bbe59e8dd2328a990@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net] [virt] INFO: task hung in __vhost_worker_flush

> Date: Sat, 30 Aug 2025 19:21:32 -0700	[thread overview]
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    11e7861d680c Merge tag 'for-linus' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c5c242580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d4703ac89d9e185a
> dashboard link: https://syzkaller.appspot.com/bug?extid=7f3bbe59e8dd2328a990
> compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1671ba62580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1685aa62580000

#syz test

--- x/drivers/vhost/vhost.c
+++ y/drivers/vhost/vhost.c
@@ -407,16 +407,14 @@ static int vhost_run_work_kthread_list(v
 	kthread_use_mm(dev->mm);
 
 	for (;;) {
-		/* mb paired w/ kthread_stop */
-		set_current_state(TASK_INTERRUPTIBLE);
-
-		if (kthread_should_stop()) {
-			__set_current_state(TASK_RUNNING);
-			break;
-		}
 		node = llist_del_all(&worker->work_list);
-		if (!node)
+		if (!node) {
+			if (kthread_should_stop())
+				break;
+			__set_current_state(TASK_INTERRUPTIBLE);
 			schedule();
+			continue;
+		}
 
 		node = llist_reverse_order(node);
 		/* make sure flag is seen after deletion */
--