From: Simon Horman <horms@kernel.org>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: netdev@vger.kernel.org, Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net v4 5/8] net/sched: netem: batch-transfer ready packets to avoid child re-entrancy
Date: Fri, 10 Apr 2026 12:39:10 +0100 [thread overview]
Message-ID: <20260410113910.GU469338@kernel.org> (raw)
In-Reply-To: <20260406172627.210894-6-stephen@networkplumber.org>
On Mon, Apr 06, 2026 at 10:25:13AM -0700, Stephen Hemminger wrote:
> netem_dequeue_child() previously transferred one packet from the tfifo
> to the child qdisc per dequeue call. Parents like HFSC that track
> class active/inactive state on qlen transitions could see an enqueue
> during dequeue, causing double-insertion into the eltree
> (CVE-2025-37890, CVE-2025-38001). Non-work-conserving children like
> TBF could also refuse to return a just-enqueued packet, making netem
> return NULL despite having backlog, which causes parents like DRR to
> incorrectly deactivate the class.
>
> Move all time-ready packets into the child before calling its dequeue.
> This separates the enqueue and dequeue phases so the parent sees
> consistent qlen transitions.
>
> Fixes: 50612537e9ab ("netem: fix classful handling")
>
nit: no blank line here
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
I forwarded an AI generated review separately.
Because I couldn't convince myself it wasn't valid.
...
next prev parent reply other threads:[~2026-04-10 11:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-06 17:25 [PATCH net v4 0/8] net/sched: netem bug fixes Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 1/8] net/sched: netem: fix probability gaps in 4-state loss model Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 2/8] net/sched: netem: fix queue limit check to include reordered packets Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 3/8] net/sched: netem: only reseed PRNG when seed is explicitly provided Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 4/8] net/sched: netem: refactor dequeue into helper functions Stephen Hemminger
2026-04-10 11:39 ` Simon Horman
2026-04-06 17:25 ` [PATCH net v4 5/8] net/sched: netem: batch-transfer ready packets to avoid child re-entrancy Stephen Hemminger
2026-04-10 11:36 ` Simon Horman
2026-04-10 11:39 ` Simon Horman [this message]
2026-04-06 17:25 ` [PATCH net v4 6/8] net/sched: netem: null-terminate tfifo linear queue tail Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 7/8] net/sched: netem: check for invalid slot range Stephen Hemminger
2026-04-06 17:25 ` [PATCH net v4 8/8] net/sched: netem: fix slot delay calculation overflow Stephen Hemminger
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