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

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Message-ID: <aHAwoPHQQJvxSiNB@pop-os.localdomain>
Date: Thu, 10 Jul 2025 14:29:04 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Xiang Mei <xmei5@....edu>
Cc: 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 Thu, Jul 10, 2025 at 03:09:42AM -0700, Xiang Mei wrote:
> A race condition can occur when 'agg' is modified in qfq_change_agg
> (called during qfq_enqueue) while other threads access it
> concurrently. For example, qfq_dump_class may trigger a NULL
> dereference, and qfq_delete_class may cause a use-after-free.
> 
> This patch addresses the issue by:
> 
> 1. Moved qfq_destroy_class into the critical section.
> 
> 2. Added sch_tree_lock protection to qfq_dump_class and
> qfq_dump_class_stats.
> 
> Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost")
> Signed-off-by: Xiang Mei <xmei5@....edu>

Reviewed-by: Cong Wang <xiyou.wangcong@...il.com>

I am looking forward to your net-next patch to make it towards RCU. :)

Thanks.