From: "Toke Høiland-Jørgensen" <toke@toke.dk>
To: Jamal Hadi Salim <jhs@mojatatu.com>, netdev@vger.kernel.org
Cc: Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@kernel.org>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
Victor Nogueira <victor@mojatatu.com>,
cake@lists.bufferbloat.net
Subject: Re: [PATCH net-next 4/4] net/sched/sch_cake: drop dead nla_nest_end() error check
Date: Thu, 08 Oct 2026 12:24:33 +0200 [thread overview]
Message-ID: <87v77csd5q.fsf@toke.dk> (raw)
In-Reply-To: <QDISC-5RTM.v1.20261007130704-5@mojatatu.com>
Jamal Hadi Salim <jhs@mojatatu.com> writes:
> cake_dump_class_stats() closes the TCA_STATS_APP nest with
>
> if (nla_nest_end(d->skb, stats) < 0)
> return -1;
>
> nla_nest_end() never returns a negative value: it has a single
> `return skb->len;` and no error path (that is why the overflow-aware
> nla_nest_end_safe() helper was later added). The '< 0' test can never
> be true, so the 'return -1' is unreachable dead code.
>
> Drop the check and close the nest with the bare statement, matching the
> sibling cake nests in the same file.
>
> This issue was discovered while fixing a bug on the gate action, see:
> https://lore.kernel.org/netdev/QDISC-H19Z.v1.20261001053234@mojatatu.com/
>
> Conditions to recreate the bug:
> - not runtime observable: the issue is found by inspection.
>
> Reviewed-by: Victor Nogueira <victor@mojatatu.com>
> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
prev parent reply other threads:[~2026-10-08 10:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-08 7:47 [PATCH net-next 0/4] net/sched: sch_cake: fixes for accounting and reconfiguration Jamal Hadi Salim
2026-10-08 7:47 ` [PATCH net-next 1/4] net/sched/sch_cake: serialize reconfiguration with the datapath Jamal Hadi Salim
2026-10-08 10:06 ` Toke Høiland-Jørgensen
2026-10-08 11:53 ` Jamal Hadi Salim
2026-10-08 12:03 ` Toke Høiland-Jørgensen
2026-10-08 7:47 ` [PATCH net-next 2/4] net/sched/sch_cake: reduce parent backlog when clearing a tin Jamal Hadi Salim
2026-10-08 10:19 ` Toke Høiland-Jørgensen
2026-10-08 7:47 ` [PATCH net-next 3/4] net/sched/sch_cake: widen buffer_used to u64 Jamal Hadi Salim
2026-10-08 10:24 ` Toke Høiland-Jørgensen
2026-10-08 7:47 ` [PATCH net-next 4/4] net/sched/sch_cake: drop dead nla_nest_end() error check Jamal Hadi Salim
2026-10-08 10:24 ` Toke Høiland-Jørgensen [this message]
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