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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jamal Hadi Salim , Jiri Pirko Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, David Ahern , Xiang Mei Subject: [PATCH net v2 1/1] net/sched: defer qdisc freeing after failed creation Date: Wed, 2 Sep 2026 23:52:31 +0800 Message-ID: <20260902155231.2149915-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260902155231.2149915-1-bestswngs@gmail.com> References: <20260902155231.2149915-1-bestswngs@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit An RTM_NEWQDISC request can make clsact bind a populated shared ingress block during ->init(), publishing an embedded mini_Qdisc to lockless readers. If the same request has an invalid TCA_RATE, estimator setup fails after ->init(); the unwind removes the pointer but synchronously frees its containing qdisc while tc_run() may still hold it. Retire failed qdiscs through the same RCU helper as normal destruction. Inline the synchronous free into the callback now that no direct callers remain. Fixes: 51ab2994c387 ("net: sched: allow ingress and clsact qdiscs to share filter blocks") Reported-by: Xiang Mei Link: https://lore.kernel.org/netdev/20260805102505.740806-1-david.lee@trailofbits.com/ Assisted-by: OpenAI-Codex:gpt-5.6 Signed-off-by: Weiming Shi --- Changes in v2: - inline qdisc_free() into qdisc_free_cb() - use qdisc_free_rcu() for normal and failed-construction teardown - use the precise 51ab2994c387 Fixes tag requested on the v1 thread - credit the earlier security-list reporter and link the public v1 include/net/sch_generic.h | 2 +- net/sched/sch_api.c | 2 +- net/sched/sch_generic.c | 20 ++++++++++---------- 3 files changed, 12 insertions(+), 12 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index cbc248776511..f35bd06a6bad 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -793,7 +793,7 @@ void qdisc_offload_query_caps(struct net_device *dev, struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, const struct Qdisc_ops *ops, struct netlink_ext_ack *extack); -void qdisc_free(struct Qdisc *qdisc); +void qdisc_free_rcu(struct Qdisc *qdisc); struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue, const struct Qdisc_ops *ops, u32 parentid, struct netlink_ext_ack *extack); diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 65b35528d125..795accd1bb33 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1382,7 +1382,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev, err_out3: qdisc_lock_uninit(sch, ops); netdev_put(dev, &sch->dev_tracker); - qdisc_free(sch); + qdisc_free_rcu(sch); err_out2: bpf_module_put(ops, ops->owner); err_out: diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index ef2b4bf51564..71630b795f9d 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -1086,21 +1086,21 @@ void qdisc_reset(struct Qdisc *qdisc) } EXPORT_SYMBOL(qdisc_reset); -void qdisc_free(struct Qdisc *qdisc) +static void qdisc_free_cb(struct rcu_head *head) { - if (qdisc_is_percpu_stats(qdisc)) { - free_percpu(qdisc->cpu_bstats); - free_percpu(qdisc->cpu_qstats); + struct Qdisc *q = container_of(head, struct Qdisc, rcu); + + if (qdisc_is_percpu_stats(q)) { + free_percpu(q->cpu_bstats); + free_percpu(q->cpu_qstats); } - kfree(qdisc); + kfree(q); } -static void qdisc_free_cb(struct rcu_head *head) +void qdisc_free_rcu(struct Qdisc *qdisc) { - struct Qdisc *q = container_of(head, struct Qdisc, rcu); - - qdisc_free(q); + call_rcu(&qdisc->rcu, qdisc_free_cb); } static void __qdisc_destroy(struct Qdisc *qdisc) @@ -1127,7 +1127,7 @@ static void __qdisc_destroy(struct Qdisc *qdisc) trace_qdisc_destroy(qdisc); - call_rcu(&qdisc->rcu, qdisc_free_cb); + qdisc_free_rcu(qdisc); } void qdisc_destroy(struct Qdisc *qdisc) -- 2.55.0