netdev - Re: [PATCH v3] net/sched: sch_qfq: Fix race condition on qfq

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Message-ID: <aHWcRp7mB-AXcFKd@xps>
Date: Mon, 14 Jul 2025 17:09:42 -0700
From: Xiang Mei <xmei5@....edu>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org,
	gregkh@...uxfoundation.org, jhs@...atatu.com, jiri@...nulli.us,
	security@...nel.org
Subject: Re: [PATCH v3] net/sched: sch_qfq: Fix race condition on
 qfq_aggregate

On Mon, Jul 14, 2025 at 03:32:23PM -0700, Jakub Kicinski wrote:
> On Sun, 13 Jul 2025 17:04:24 -0700 Xiang Mei wrote:
> > Please let me know if I made any mistake while testing:
> > 1) Apply the patch to an lts version ( I used 6.6.97)
> 
> Please test net/main, rather than LTS:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/

Thanks for the information. I re-tested on the latest version of net/main,
which contained my patch, but it doesn't crash on 5e6d. I re-verified 
this patch and can't connect it with a null-deref in dequeue.


Here is more information no how I tested:

1) I ran `python3 ./tdc.py -f ./tc-tests/infra/qdiscs.json -e 5e6d` 100
times
2) The KASAN is enabled, and my patch is on it
3) All 100 results show `ok 1 5e6d - Test QFQ's enqueue reentrant behaviour
with netem` without any crashing in dmesg

I may need more information to trace this crash.