netdev - Re: [PATCH v3] net/sched: sch_qfq: Fix null-deref in agg

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Message-ID: <aGnodC+JgY8wI9xc@pop-os.localdomain>
Date: Sat, 5 Jul 2025 20:07:32 -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 null-deref in agg_dequeue

On Sat, Jul 05, 2025 at 02:21:43PM -0700, Xiang Mei wrote:
> 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. Changed qdisc_warn_nonwc(include/net/pkt_sched.h) into a static
> inline function.
> 
> 2. Moved qdisc_peek_len from net/sched/sch_hfsc.c to
> include/net/pkt_sched.h so that sch_qfq can reuse it.
> 
> 3. Applied qdisc_peek_len in agg_dequeue to avoid crashing.
> 
> Signed-off-by: Xiang Mei <xmei5@....edu>

Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost")
Reviewed-by: Cong Wang <xiyou.wangcong@...il.com>

Thanks!