From: Victor Nogueira <victor@mojatatu.com>
To: hexlabsecurity@proton.me,
Vinicius Costa Gomes <vinicius.gomes@intel.com>,
Paolo Abeni <pabeni@redhat.com>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>, Jakub Kicinski <kuba@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>
Cc: Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, Jarek Poplawski <jarkao2@gmail.com>,
Vladimir Oltean <vladimir.oltean@nxp.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] net/sched: sch_multiq: Replace direct dequeue call with peek and qdisc_dequeue_peeked
Date: Fri, 26 Jun 2026 14:18:01 -0300 [thread overview]
Message-ID: <fc1b9963-2f69-4e47-bf59-6b668faedc0e@mojatatu.com> (raw)
In-Reply-To: <20260625-b4-disp-31bcb279-v1-2-85c40b83c529@proton.me>
On 25/06/2026 06:51, Bryam Vargas via B4 Relay wrote:
> From: Bryam Vargas <hexlabsecurity@proton.me>
>
> multiq_dequeue() takes a packet from a band's child with a direct
> ->dequeue() call after multiq_peek() peeked it. When the child is
> non-work-conserving the peek stashes the skb in the child's gso_skb, so
> the direct dequeue returns a different skb and orphans the stash,
> desyncing the child's qlen/backlog. With a qfq child reached through a
> peeking parent (e.g. tbf) this re-enters the child on an emptied list and
> dereferences NULL, panicking the kernel from softirq on ordinary egress.
>
> Take the packet through qdisc_dequeue_peeked(), as sch_prio already does
> and as sch_red and sch_sfb were just fixed to do. The helper is a no-op
> when the child has no stash, so a work-conserving child is unaffected.
>
> Fixes: 77be155cba4e ("pkt_sched: Add peek emulation for non-work-conserving qdiscs.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
next prev parent reply other threads:[~2026-06-26 17:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-25 9:51 [PATCH 0/2] net/sched: finish the qdisc_dequeue_peeked conversion (taprio, multiq) Bryam Vargas via B4 Relay
2026-06-25 9:51 ` [PATCH 1/2] net/sched: sch_taprio: Replace direct dequeue call with peek and qdisc_dequeue_peeked Bryam Vargas via B4 Relay
2026-06-26 17:16 ` Victor Nogueira
2026-06-26 17:46 ` Jamal Hadi Salim
2026-06-25 9:51 ` [PATCH 2/2] net/sched: sch_multiq: " Bryam Vargas via B4 Relay
2026-06-26 17:18 ` Victor Nogueira [this message]
2026-06-26 17:47 ` Jamal Hadi Salim
2026-06-27 2:00 ` [PATCH 0/2] net/sched: finish the qdisc_dequeue_peeked conversion (taprio, multiq) patchwork-bot+netdevbpf
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