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Date: Wed, 2 Jul 2025 07:40:58 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Xiang Mei <xmei5@asu.edu>
Cc: xiyou.wangcong@gmail.com, netdev@vger.kernel.org, jhs@mojatatu.com,
	jiri@resnulli.us, security@kernel.org
Subject: Re: [PATCH] net/sched: sch_qfq: Fix null-deref in agg_dequeue
Message-ID: <2025070231-unrented-sulfate-8b6f@gregkh>
References: <CAM_iQpWkQd_1BdP+4cA2uQ5HP2wrb5dh8ZUgGWY7v3enLq_7Fg@mail.gmail.com>
 <20250702040228.8002-1-xmei5@asu.edu>
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On Tue, Jul 01, 2025 at 09:02:28PM -0700, Xiang Mei wrote:
> From: n132 <xmei5@asu.edu>
> 
> To prevent a potential crash in agg_dequeue (net/sched/sch_qfq.c)
> when cl->qdisc->ops->peek(cl->qdisc) returns NULL, we check the return
> value before using it, similar to the existing approach in sch_hfsc.c.
> 
> To avoid code duplication, the following changes are made:
> 
> 1. Moved qdisc_warn_nonwc to include/net/sch_generic.h and removed
> its EXPORT_SYMBOL declaration, since all users include the header.
> 
> 2. Moved qdisc_peek_len from net/sched/sch_hfsc.c to
> include/net/sch_generic.h so that sch_qfq can reuse it.
> 
> 3. Applied qdisc_peek_len in agg_dequeue to avoid crashing.
> 
> Signed-off-by: n132 <xmei5@asu.edu>

We need a real name, sorry.  Please read the documentation for why.

thanks,

greg k-h