linux-kernel - Re: [PATCH V2] net/sched: Prevent notify to parent who unsupport class ops

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Message-ID: <aGizFhZwnPo98Bj/@pop-os.localdomain>
Date: Fri, 4 Jul 2025 22:07:34 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org,
	jhs@...atatu.com, jiri@...nulli.us, kuba@...nel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V2] net/sched: Prevent notify to parent who unsupport
 class ops

Hi Lizhi,

On Sat, Jul 05, 2025 at 09:18:22AM +0800, Lizhi Xu wrote:
> If the parent qdisc does not support class operations then exit notify.
> 
> In addition, the validity of the cl value is judged before executing the
> notify. Similarly, the notify is exited when the address represented by
> its value is invalid.
> 
> Reported-by: syzbot+1261670bbdefc5485a06@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1261670bbdefc5485a06

Maybe I didn't make it clear, I think Victor's patch also fixes this
bug.

https://lore.kernel.org/netdev/20250704163422.160424-1-victor@mojatatu.com/

Can you check if you still see the crash with his fix?

The reason why I am asking is because his fix addresses a problem
earlier on the code path, which possibly makes your fix unnecessary.
Hence, his fix is closer to the root cause.

Please test and confirm.

Thanks!