netdev - Re: [REGRESSION] 6.14.3 panic - kernel NULL pointer dereference in htb

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Message-ID: <aA6BcLENWhE4pQCa@pop-os.localdomain>
Date: Sun, 27 Apr 2025 12:11:45 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: "Alan J. Wylie" <alan@...ie.me.uk>
Cc: Holger Hoffstätte <holger@...lied-asynchrony.com>,
	Jamal Hadi Salim <jhs@...atatu.com>, regressions@...ts.linux.dev,
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Octavian Purdila <tavip@...gle.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	stable@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [REGRESSION] 6.14.3 panic - kernel NULL pointer dereference in
 htb_dequeue

Hi Alan,

On Thu, Apr 24, 2025 at 01:53:31PM +0100, Alan J. Wylie wrote:
> > On Tue, Apr 22, 2025 at 07:20:24PM +0200, Holger Hoffstätte wrote:
> 
> > Meanwhile, if you could provide a reliable (and ideally minimum)
> > reproducer, it would help me a lot to debug.
> 
> I've found a reproducer. Below is a stripped down version of the shell script
> that I posted in my initial report.
> 
> Running this in a 1 second loop is enough to cause the panic very quickly.
> 
> It seems a bit of network traffic is needed, too.
> 

I just tried your reproducer in my VM since I don't have pppoe setup,
after running ping flood (ping -f) bidirectionally for ~10 minutes, I
still didn't get any warning or crash.

I also tried to reduce the bandwidth limit you set in your script to get
traffic throttled, still no crash/warning.

Note, I just used the latest -net, without applying any extra patch.

Thanks!